You are talking about a rent-to-own otherwise known as a lease option. Nothing is written in stone about the terms. You can apply a portion of their rent to the purchase price or you don't have to. Usually when I do a lease option, I do apply the initial option fee to the purchase. But I do not apply the rent to the purchase price unless they are paying an amount higher than the going rent for the area. For example, if the going rent is $850 but they are paying $1000, then I would apply the extra $150 to their purchase price and might agree to match it with an additional $150. Like I said, there are no set rules about rent-to-own. It is whatever you and the tenant agree to.
Kathy Persha, Assoc.Broker/Realtor/Investor
Keller Williams Realty
GRI, CDPE, SFR, CIAS