Find a good all-purpose real estate sales contract.
Almost any real estate agent can give you a copy of the one his or her company uses. You can also look on the Internet for state-specific forms. Usually there is a small fee for downloading the forms from one of these websites.
Beware of forms that claim to be applicable in all jurisdictions. Most states have their own very specific requirements regarding what must be included in a real estate sales contract and the disclosures that must accompany that contract.
Pay particular attention to any consumer protection laws related to preforeclosure purchases. A real estate agent form will not include those provisions.