Heartworm medicine costs more, shots can sometimes be more costly, etc. A Mastiff needs obedience training. It is imperative that obedience training be done. After all do you want to be pulled down the street legs streaming behind you when your 185 lb. The obedience training must be the positive reinforcement type.
Mastiffs respond well to love, praise, and especially treats.
The training should not be negatively based nor should it be the type where the dog is jerked around using different types of collars. Exercising a Mastiff is not as difficult as exercising one of the various sporting breeds who seem to have endless energy. A Mastiff is happy to go on 2 walks a day of about 20 - 30 minutes. They will not jog and should not be asked to as it can be very difficult on their joints. About a mile or so walk twice a day is enough unless it's an older Mastiff, then play it by ear.