Regulations on this will differ by state. The best move would be to find a local real estate lawyer. They wil instruct you on how to file all the proper paperwork with the local government, and also advise you on things you haven't thought about, like how to structure your wills to make sure everyone is protected in the event something unfortunate happens to either of you.
Also don't use this private transaction as an excuse to save money to skip any steps. Go get the title search and inspection done. You don't want any surprises. If the inspection finds a fundamental problem, you might still go through with the purchase, but at least you'll know up front what you're in for.