I highly recommend you call and talk with Dave Setti with Turnkey Mortgage. He'll run your scenario with you to see what your options are. You will have to qualify for the new mortgage based on the lending criteria of turning your current home into a rental. Lenders don't count 100% of the rent to off set your mortgage and some of them require a one year lease and canceled check from a renter prior to funding and closing on your next loan.
Having an honest discussion with the lender up front may save you money and potential heart ache later.
Have an amazing day.