How long must I live in a house once I buy?

When you apply for a loan, a lender will ask if you intend to use the property as a prime residence.  If the answer is "yes," then it is expected that you will physically move into the property and live there for some time.  There does not seem to be a set definition in the term "some time," but what lenders are getting at is this:  They do not want to make residential loans with low rates and little down to investors. 

Thus, if someone gets a residential mortgage, instantly moves out, and quickly rents the place, lenders will be more than unhappy - they may call the loan.  They may also review the loan application to see if fraud was involved.  Lenders do not want borrowers to move in and then rapidly move out, but they will look at the "facts and circumstances" if such an event occurs.  For instance, a sudden job change not known in advance might be a valid reason for a move after several months of occupancy.  What lenders do not want are situations where a "residential" borrower is actually a disguised investor.  Given that most homes are occupied for 8-10 years, a move after several months or a year is likely to set off bells. 

 Make sure that you ask the lender if there is a prepayment penalty and if there is how long does it last.  Also be sure you know how much it is.  Most are based on the principal amount left on the loan.  If that's the case.  Try to lower your principal amount before you pay the loan off that will help minimize your penalty.