What is the 12 month occupancy guideline?  The 12 month occupancy guideline states if
borrower has taken out a mortgage on a Primary Residence within the last 12 months, then
a new mortgage would have to be treated as Non-Owner Occupied.   If you did a conforming 
conventional loan,  at closing you most likely signed The Uniform Deed of Trust for Fannie
Mae and Freddie Mac.  It states: “Borrower shall occupy, establish, and use the Property
as Borrower’s principal residence within 60 days after the execution of this Security Instrument
and shall continue to occupy the Property as Borrower’s principal residence for at least one year
after the date of occupancy, unless Lender otherwise agrees in writing, which consent shall not be unreasonably withheld, or unless extenuating circumstances exist which are beyond Borrower’s control…. “  

By signing this document, the borrower acknowledges and agrees to occupy the residence for a minimum of 12 months.  Even if you did not sign a document containing above language, most
lenders will have the 12 month occupancy rule as an overlay.  Therefore, this is difficult to avoid
unless you sell the property outright or wait to purchase after the 12 month is up.  If you keep the property and rent it, then the 12 month rule will apply unless extenuating circumstances exist.  Otherwise, you will be required to purchase your new home as an investment property with
20% down payment and a higher interest rate.

Move up buyers should be cautious when looking to upgrade to a larger home within the same
year that they financed a primary residence.   If this is going to be the case, then you should
consider funding the existing residence as an investment property to avoid this issue.