Welcome aboard and congrats on your new family member~ Mastiffs need to be near their family. Personally, I would not house a pup outside especially a mastiff. The pup can be outside when weather permits for as long as they want to hang out outside but not to permanently house them outside.
The following tips/suggestions are based on my experience as a dog mommy, forum member*s posts and volunteering at an animal shelter for a year.
*CRATE THE PUP
You want to crate train the pup. Make sure you have a blanket, stuffed animal (about their size) and white noise (ticking clock or ipod with soft music) so the pup can sleep. The pup is used to cuddling with siblings.
Make the crate the pup*s happy place to go to when he wants to sleep, decompress or just hang out.
*SECURE THE PUP NEAR THE FAMILY
You want to keep the pup in a room with a family member. Mastiffs need to be near their family members.
*FOOD
Find out what kind of food the shelter/rescue/breeder was feeding the pup and continue to feed it to the pup until you transition to a newer food because most shelters/rescues/breeders use the cheapest food, meaning it is not very good for the pup.
Slow transition to the new food is as follows to prevent diarrhea. If at any time during the transition, the pup has diarrhea return to previous amounts of food per feeding. If you are switching flavors made by the same manufacturer, you should not have to do a slow transition.
Amount per feeding:
Day 1-4 ¾ cup of old food and ¼ cup of new food.
Day 5-9 ½ cup of old food and ½ cup of new food.
Day 10-14 ¾ cup of new food and ¼ cup of old food
Day 15 Start 100% of new food
OR
You can feed the pup boiled meat and boiled white rice with canned/raw pumpkin (not the pie filling) usually start with 1 teaspoon or the pumpkin for young puppies and 1-2 tablespoons of pumpkin for pups older than 8-10 months for 4-5 days to reset their system. After the reset, start the new food.
Generally, mastiffs are allergic to grain and chicken found in kibble. You can check
www.dogfoodadvisor.com for dog food ratings and customer feedback. Mastiff puppies should eat Large Breed adult food or All Stage food because puppy food has too much calcium which causes fast growth. Slow and steady growth for a healthy mastiff. Protein in the food is not an issue unless the pup has kidney issues.
http://www.peteducation.com/article.cfm?c=2+1659&aid=652
http://www.drsfostersmith.com/pic/article.cfm?aid=459
Check out Acana Regionals, Wellness Core, Castor & Pollux Grain Free, Earthborn Holistics, Fromm*s, Innova Natures Table, Victor*s Grain Free or Taste of the Wild grain free. Chewy.com is a great place to order dog food and they offer free shipping.
You may want to check out the raw diet for your pup. Raw diet can be fed to young pups. Check out the sub forum on raw diet that has a wealth of information. It is not recommended to feed the pup kibble (one with grains) and raw food. Do your research re: raw diet and form your own opinion.
*PUP NOT EATING WHEN YOU FIRST BRING THEM HOME
They are not used to their new environment and this is a natural behavior. Take the pup to a quiet place at meal times and sit and hand feed the pup. This will help the pup to eat when they are placed in a calm atmosphere, help you to bond with the pup and help the pup establish trust with you. As they become settled, they will naturally follow your routine.
*PROTECT THE PUP FROM DISEASE
Keep the pup in your yard and place newspapers down where they will walk on the ground. Keep the pup away from dog areas unless they have had their 2nd round of shots, 3[SUP]rd[/SUP] round of shots is best so they will have some immunity to the infectious diseases, i.e. Parvo. This is very important!
*HOUSE TRAINING YOUR PUP
Keep pup on leash when you take them outside. Train them with a potty word, like “potty.” Generally, it takes a pup 20-25 minutes to do their business. When the pup goes potty, do the potty dance. The potty dance is a dance while you are singing the pup*s praises for going potty. It works!
http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/house-training-your-puppy
*SOCIALIZE, SOCIALIZE AND SOCIALIZE SOME MORE
Socialize after they*ve had at least 2 round of shots preferably 3 rounds of shots to be safe. Prior to the 2[SUP]nd[/SUP] or 3[SUP]rd[/SUP] round of shots, keep the pup in your own yard. If that is not possible, bring newspapers with you for the pup to walk on. Avoid dog parks and areas with a heavy traffic of animals.
Socialization can be the human park while the pup is on leash, riding in the car, sitting at the park or shopping center/mall, etc.
Tell strangers and strangers with pups “no touch, no talk, no look” at your pup as they approach. Bring your pup to sit while they approach. Have your pup approach the strangers and allow the pup to sniff them. Have a calm, controlled meeting. This shows your pup the correct way to greet strangers and other pups.
*TRAINING YOUR PUP
Start basic commands and reward with motivational treats (fav food or fav toy). Train for about 5 minutes per day and slowly increase the training time. Teach one command at a time. Once they master one command, move onto another command.
Number one command is sit. Teach the pup to sit, by placing a treat in front of his head and move it to the back causing him to sit to get the treat. When the pup sits, tell them good sit and give them the treat.
Second command should be "focus/look" This will help you tremendously when the pup is over 100 lbs. Put the pup into sit. With a treat in your hand (let the pup smell it), put the treat up to your eyes and tell the pup to look or focus. They may only do this for about 1-2 seconds. As soon as they look at your eyes, reward them. Generally, mastiffs do not like to look anyone in the eyes for long because that means a challenge to them.
Other commands are "down/off", "leave it," "wait" (short pause), "stay" (pausing until you release), drop it and "quiet/calm".
When you are training and when the pup does not do as you ask, then tell him “no” in a calm, stern voice and redirect back to the command. The only time a stern and loud NO should be used is when they are doing something that can cause harm to themselves or others.
Praise is the most powerful tool you have and the dog WANTS to please you. Show them clearly what you want, notice and praise when they comply, and learning goes much faster and pleasant for you both.
Mastiffs can be extremely stubborn and if you get frustrated with them, they will shut down and stop listening to you. Mastiffs do not do well with yelling or hitting. Hitting can result in some unwanted mastiff behavior meaning fear aggression, which equals biting.
*LEASH TRAINING
Have the wear the leash around the house to get used to it. Once they are used to the leash around their neck, then you can start the leash training. Have lots of motivational rewards on hand while doing the training. Consistency and patience is key.
If the dog pulls, do not walk until they stop and turn to look at you, then thank them with a motivational reward and start walking again. Tell him it's ok to walk by you start walking. When you have to stop, tell him stop or wait and tell him sit. Titan knows that when we are walking and I say, "wait," he has to stop and sit and wait for me to begin walking again. Requires a lot of consistent training and patience. Do this inside the house and then move to outside.
If they nip at you because they want to play, do the same. Stop, sit and wait. Reward the dog with motivational reward when they do the commands.
*PUPPY BITING/NIPPING/AROUND CHILDREN
Puppies will chew/bite anything they can find unless you re-direct the chewing/biting. Provide frozen washcloths or small towels (make sure the cloths are big enough the pup cannot swallow them), ice cubes with treats frozen in the middle, nylabones, ropes, deer antlers, Kongs with frozen yogurt so they can chew to their heart*s desire. Some people use boxes, be aware that the pup will continue to chew all boxes.
If you puppy is biting/nipping, then try the following. This behavior can sometimes take a lot of patience and consistency in training.
They bite and growl because that is how they played with their siblings.
When they bite, tell them “OW” in a high-pitched voice and “NO” in a stern, calm voice. NEVER HIT OR YELL AT A MASTIFF. Hitting can lead to fear aggression and yelling causes the pup to shut down on you and ignore you.
When the pup stops biting, tell them to sit and re-direct to one of the chew toys.
Teach the pup “leave it” is another option. When the pup “leaves it” meaning your body part that he is biting, then bring to a sit and reward with motivational reward.
**Do not allow children and pup on the floor together. Pup will see them as playmates and nip at them. Picture the pup playing with their siblings.
Keep the pup on leash while the children are on the floor so you can have control of the pup. Pup and children should not be allowed to play alone.
Have the children hand fed the pup and help with training, i.e. teach the pup to sit, stay and come. This helps the pup to see them as non-playmates but as people in authority. These activities are great bonding exercises.
*EXERCISE
Puppies can exercise with natural movements and free play like running, stretching, playing on soft surfaces (grass and dirt). This type of exercise is actually healthy and good for their developing bodies but they do need to be able to pace themselves.
Structured exercise/play on hard surfaces and where they don't have they ability to pace themselves is where you need to be very careful. This type of exercise could harm the pup*s joints and bones. Puppies should not do any excessive exercise, i.e. walking, jumping, running and navigate stairs for the first 12 months to avoid injury.
Stairs should be maneuvered while on leash (even in the house) especially going down the stairs. Stairs should have carpet or rubber matting to give the pup traction. Mastiffs should be assisted up and down stairs until they are about age 12 months to prevent injury.
Most mastiffs can be very lazy but they still need to exercise. Generally, the amount of time to exercise is 5 minutes per each month of age.
*YOUR PUP AND HEAT (NOT THE FEMALE HEAT)
Remember, mastiffs do not tolerate heat. In the heat, reduce walk/exercise times. Have clean water available at all times. I freeze towels to either place on Titan or put on the floor for him to lie on in the summer to cool him off. Buy a kiddies* pool for the pup to play in to keep cool.
*DE-SEXING YOUR PUP
Mastiffs should not be neutered/spayed until 18 months to 2 years.
NO MATTER what the vet says. Early neutering can cause growth problems and health issues. **Remember, you must be a very responsible dog owner to not neuter your pet to prevent unwanted pregnancies.**
Health Issues Linked to Spaying and Neutering Dogs
Enjoy your baby! Have lots of patience! The pup will reward you with love and loyalty!
While I'm of course nowhere near an expert, I will share with you how we've been working things. My SO and I both work full time, so we unfortunately have to keep Duke in his kennel during the day and have not been able to go home and let him out mid-day. While we recognize this is not ideal, until he is potty trained it's how it will roll! He had one accident in his kennel the very first night and hasn't had one since! We have been very fortunate, but he holds it for a WHILE when he's in his crate. You're very fortunate to have time at home during the weekdays to spend with a puppy - I wish I had that! 
