In all states in this country a person owning real estate in his or her name must be at least 18 years of age, an adult. If your fiance' is 17 years of age, she cannot legally sign any loan documents to purchase the house since she is a minor.If she want to be placed on title to the home, while she is 17, either a guardianship or trust must be established for her where the guardian or trustee takes title for her while she is under 18 years of age. When she turn 18, title to the property can then be placed in her name. I suggest you hold off placing title to the home in her name for now and when she turns 18 then her name can go on record for the property by either a grant or quit claim deed.Good luck.