I need a special buy/sell contract

[Stephen Gilmore]

Hello everyone, I am looking a tax sale lot that is next to a house. I have already spoken with the person that owns the house and they want to buy the lot through me. I have done this before with success but this one is a little different. Before if the person backed out on me I could still sell the lot to someone else. The one I'm looking at now is situated to where I believe that only that person with the house next to it would want it. I do not believe they would back out on me but if they did I would probably be stuck with it. So I would like to come up with some kind of contract stating that I agree to sell to them and they agree to buy from me etc. However, if I was to do that I would need something in the contract for me to back out of the situation if I was not awarded the property. Has anyone done this before or know if a simple contract I could get written up with an out for me without saying, "I will sale this lot to you as long as I am able to purchase it first"? I wouldn't say it like that of course but don't want to give away that it's something they can go do themselves too. I am not sure how to word it to where I protect myself and also not give away that I do not actually own the lot yet. Thanks for reading and any thoughts would be most appreciated.