Do you want a Letter of Intent to purchase the property? That is something you can do if you know your contingencies. But if you are negotiating the purchase, you should work with your real estate attorney. He will negotiate all the terms in your favor.
The LOI will have to have the name of the buyer, address, phones, who will be the closing attorney or broker
how much you will pay, earnest money if any, down payment, amount at closing, days to close, days for due diligence, contingencies such as subject to xxx mortgage, delivered vacant, engineer report, etc, etc. I can send you a very simple one if you want a guide. email@example.com
Apr 7, 2015