Rent-to-own contracts let the renter buy the property he is renting at the end of the lease term if he chooses. In many cases, the paperwork for these agreements is almost the same for a lease, with the exception of purchase clauses. For this reason, the method for getting out of a rent-to-own contract is fairly the same as for getting out of a regular lease.
Review your rent-to-own contract for termination situations. The contract may be void if the person from whom you're renting has done something contrary to the contract terms. Present these issues to the property owner if you find any.
Talk to the person from whom your renting. Ask if she would be willing to let you out of the contract free and clear -- she likely won't, but you can improve the odds of agreement if you can show how terminating the contract would be mutually beneficial.
Ask the property owner if he will accept a buyout fee in order to terminate the agreement. In some instances, a buyout fee is included in the contract, but if it isn't and your property owner agrees to a buyout, you'll need to get the terms of the buyout in writing.
Inquire whether you can get someone to take over your contract, if the contract permits this action. This is essentially the same as finding a subleasor on a regular lease.
Get the terms for your contract termination in writing; if you've found someone to take over the contract, you'll need an addendum that states the new renter is agreeing to rent from the property owner instead of you. Sign all documentation, and get a copy for your records.
Pay any fees associated with early termination.
Return the property back to its original condition, complete a move-out inspection, and give the keys back to the property owner.