I've already got somebody lined up who wants to buy my house. I want to sell my house. Seems easy enough, right?

The question is how I'm supposed to make everything actually happen. There are a few web sites willing to sell me blank contracts for $15, but I don't get to see them before I pay to know whether they're any good or not. I tried calling BuyOwner.com, who advertises heavily on TV around here, and they said that they don't offer that sort of service. They require you to buy the whole package (advertising, etc.).

Anyone done this before? I imagine it's different from state to state, but I just want to figure out how to do it and get it done.