[axvk]

Even a contract doesn't really guarantee anything because it will probably never be worth it to get a lawyer and deal with suing them.

Just make sure they pay you regularly and if they want to pay when everything is finished then get a down payment. Don't let it get to the point where they owe you a lot of money because you never know if they'll pay. Try to not create a situation where if they don't pay the amount they owe you then it will really hurt you.