You might want to try LegalZoom, or just google with search terms particular to your needs.
Keep in mind that a contract is really only as good as the paper that it's written on. If they breach, you still have to take action to collect.
My advice is to get a deposit up front, or perhaps full payment. Offer the contract to make them feel protected and to add to your credibility. Try to take control of the situation as early as possible. Be persuasive, but not sketchy or forceful.
"The first lesson of economics is scarcity: there is never enough of anything to fully satisfy all those who want it. The first lesson of politics is to disregard the first lesson of economics." Thomas Sowell