Wouldn't that be an option? Options are a good method to put down a small stake on something you want the other person to be committed to sell, but only when you are ready to buy it, if ever. It's a payment to protect a first right of refusal. Not sure that it applies in this case. Options can be sold, and, in fact, can be profitable it appears that others want into the final purchase but have been locked out. On the other hand, it's a high risk.