Your boyfriend's rental history doesn't matter. If his credit is actually very good, there's only one other thing the two of you need, and that's a larger down payment. You're close now. Ideally, you want 20% down, if not 25%. Between the two of you, perhaps you can save that in a year. Get an inexpensive apartment, or rent a mobile home, and save every penny. Cook all your meals. Mostly spaghetti or sandwiches. Bring leftovers to work for lunch. Stop getting new clothes. Do errands and commuting by bicycle instead of driving, whenever possible.
By the way, are you presently paying the rent and sharing a place with your mother? What will happen to her if you move out?
Oh - be very careful if considering a rent-to-own situation. Some are dodgy, an excuse to charge you more, when the landlord is still free to back out of the deal.