Generally speaking, in order to get paid, one has to have a very well written - then signed contract.
If the contract has holes, and this goes to court, you may never get paid.
I recommend to all contractors a Construction Contract Lawyer. This guy knows the local courts and is extremely well versed at writing contracts that work.
Remember, contracts do not always mean you will get paid. It means you have a much better chance of getting paid.
Without a contract, it is difficult at best to get paid and may cost too much to even think of following through.
Even lien laws are different from state to state. A good construction lawyer is the best answer and developing a relationship with one will ultimately be very rewarding for the contractor, even though so many think it is too expensive to do so.