Look for
Payments tied to milestones, a delivery date with a penalty or refund, which law applies, what happens if the project stops, and who holds the title until handover.
Warning signs
Payments by calendar date, no penalty for delay, the right for the developer to change the design or price, and disputes only in a far-away court.
Your role
You don't give legal advice. You flag what is missing so the buyer can ask their own lawyer.
Exercise
Read a sample contract and list the five clauses above, or note that they're missing.