You'd get a new home loan.
Depending upon how your rent to own (I prefer Lease with Option to Purchase) is constructed out.
The way we do ours involves a recorded option, and a portion of lease towards the purchase principle price.
At the end of the contract, the buyer has the 'Option' to purchase with funds credited towards the purchase amount that was agreed at the beginning of the lease option contract.
I LOVE lease option purchasing. As it gives you a sort of one way valve to purchase, in that if the value goes down, you didn't throw a bunch of equity or credit, and can walk away with minimal loss. If the value goes up, you have your option recorded, and you get to walk into equity.
[Self Promotion Start:] I have a few lease option properties in California, let me know if you ever find yourself in the southern california area, [end of self promotion]
Take a look at the video link I have that shows the benefits to Buyers with seller financing through Lease Options (third party link to a third party source I quote often).