In the proceeding simply known as foreclosure (or, perhaps, distinguished as "judicial foreclosure"), the lender must sue the defaulting borrower in state court. Upon final judgment (usually summary judgment) in the lender's favor, the property is subject to auction by the county sheriff or some other officer of the court. Many states require this sort of proceeding in some or all cases of foreclosure to protect any equity the debtor may have in the property, in case the value of the debt being foreclosed on is substantially less than the market value of the real property; this also discourages a strategic foreclosure by a lender who wants to obtain the property. In this foreclosure, the sheriff then issues a deed to the winning bidder at auction. Banks and other institutional lenders may bid in the amount of the owed debt at the sale but there are a number of other factors that may influence the bid, and if no other buyers step forward the lender receives title to the real property in return.
Just remember, you will need to get the seller to agree on not only the rent to own agreement, but the terms of the agreement. i. e., length of the agreement, usually, one to two years; the percentage of the rent which gets applied to the sales price or closing costs, etc. If you get lucky, the seller may also be interested in doing Seller Financing with you. Just be sure to have a lawyer review any agreement before you sign it. A little legal cost upfront could save you thousands of dollars down the road.