Dana, I think you need to be very sure of the terms you are using and exactly what they mean.
There are "rent to own" contracts that mean that you are simply renting the home but that the owner is putting some portion of your rent into an account so that you accumilate enough money to purchase the home if you decide to do that at some time in the future. It is not a purchase: he retains full ownership.
There are also "lease with option to buy" contracts, installment sale contracts, and true lease purchase agreements. All of these have different implications and the way they are used seems to vary from one place to another.
Be sure that you have somebody who knows what type of contract you are signing, and exactly what it means to you if things don't go as planned. (especially if you don't trust the other party in the first place.)
If you have $10,000 to put down, might it be better for you to write a standard agreement of sale? Or is he willing to let you buy the home and pay the balance over some period of time at a reasonable interest rate? By that I mean, will he "take back" a mortgage for some portion of the purchase price? Then you would be the true owner as I understand it, but could be required to give the property back to him if you don't make the payments.
One more thing for you to ask your professional to explain is the difference between "owner in deed" and "owner of record". If you are not the true owner of the property be sure that he is paying the taxes, etc.
You have a lot to think about....Get some good help. There is too much money and too much risk for you to try to go it alone on this one.
Eileen Musser, (a Realtor, but also an investor who has used a number of these vehicles to buy and sell property) NOT A LAWYER, yada yada