TREC forms can only be used by licensed real estate agents. Same for TAR. Enforceable is a matter of getting the terms done properly to the point where specific performance on both sides can occur.
If your buyer gets an attorney as they should you'll be in a position of having to negotiate against an attorney and they won't do that typically and you might be attempting to practice law. You're better off hiring an attorney.
As TREC and TAR forms say
24. CONSULT AN ATTORNEY BEFORE SIGNING: TREC rules prohibit real estate license holders
from giving legal advice. READ THIS CONTRACT CAREFULLY.
Aug 31, 2017