I mean no disrespect and no insult to your family at all but really it is MORE important that you have an attorney to represent you in this transaction than with a commercial lender.  With a commercial lender the bank's attorneys will make sure that the property is free of encumbrances and that everything is legal.  Here you have no one to protect you in the event that there are violations against the property and something that is just not right with the title, etc.  So I beg you: do not prepare the contract on your own and please get a title search and a survey done and allow yourself some outs in the event that things are not as they seem.  Good luck to you.