A couple decided to sell their house in Washington D.C. without the aid of a r

A couple decided to sell their house in Washington D.C. without the aid of a real estate broker. Their asking price was $225000 which they believed was
about $15000 less than the price they would need to list the property with a broker. They realized they would probably have to accept an offer as low as
$220000. Another couple looked at the house liked it and offered to buy it for $223500. The sellers were delighted and suggested that they would fill
in the blanks on a form sales contract used by many of the local real estate brokerage firms and both parties could sign it. The buyers however
objected saying they preferred to write their own contract. The wife was an attorney who worked for the U.S. State Department specializing in
international law.

What advice would you have given the sellers?