Owner Listing - How to Take Offer/Earnest Money

[Grace Porritt]

I place a property on LoopNet and I already have an interested buyer for $520,000 (my listing price). H2e wants to have the first option to purchase and see if he can put together financing.  I told him I would take $500 to give him that opportunity.  I told him he could have the money back, if the deal does not work.  I do not want to give him too long....others are interested.  I am not sure if this would be called earnest money or something else.

Can someone help me with some wording for a receipt?  I just want to give him a couple of weeks for a more solid contract/agreement.  I am looking at doing a 1031. 

Thanks in advance.