I am not sure about what state or where you are located but one thing is to file a lien on the property owner for the work you completed. This will put you in line for payment or the owner may be forced to pay you off for your work. But it all depends on what your laws state. You will need to keep copies of your proof of work completed. Hope this helps a little. Good luck
Depends on the contract and why he isn t paying. You should have an attorney review your contracts before signing them and consult an attorney on this issue. If you can t afford an attorney and are in US I may be able to help. Just email me.