How do I get paid

Gather any evidence that you have of time worked, estimates, or just document all the work that you did and file suit in a small claims court. Then remember next time to always give a signature before you do any work. Hopefully he won't lie in court! Good luck!

Is there a document he signed saying, he agrees to the $6,000 of work? if so, that will help in your favor.

you might need to take any and all documents and receipts that prove he authorized the repair and hired you to fix it, and take him to small claims court over the $6000

Did you file a 20 Day Preliminary Notice? This is to be filed at the start of the job. This lets the owner of the property know that you will place a lein on his property if he fails to pay. What about a contract, did your client to sign a contract. What about a bid for the job. At anytime did you pull a permit for the work being done? If you had pulled a permit for the job you would have found out the person requesting the work was not the owner. The city can give you the name of the owner of the property and his address or you can find it on the internet also. Go to www.firstgov.org, under your state you will find county/city accessor where you can get the name of owner of property using address of the property you did the work at.

Once you have the name and address of the owner, write him a letter explaining your situation in full detail that you were hired to do this job it was x amount for materials x amount for your labor etc., and that you have not been paid. Request payment for the job.

Mail this letter to the owner at the address were the work was done and mail a copy of the same letter to the address you find for the owner (from the city or your own investigation) most likely there is another address for him since he isn't at the property you worked at. Send these letters requesting payment " certified mail with return receipt" only. He will have to sign for it and you should get the receipt back promptly signed. Or if the letter was undelivered they will return the letter to you. If that is the case then he either refused to accept the letter or the postoffice couldn't deliver for some reason. The post office will continue to try to deliver the certified mail for sometime and this letter can be tracked by postoffice to find out the status of it. If that doesn't work then go to court. Small Claims in California is $5000 maximum.

Get your paperwork in order anything you have pertaining to the job. Notes, material receipts, labor, names of employees or helpers, copies of the request for payment you mailed. Everything. Try to remember when you spoke to this guy who hired you and what was said, etc. Was there anyone else present or did anyone else witness any conversations?
File in Small Claims Court. Follow the instructions for this exactly. If you need to get help with legal aid it is available.

You should file on the owner of the property also along with the guy who hired you to do the work. If you had any employees or witness to job bring them to court with you.

When working on property not owned by the person requesting the work to be done, you must
get permision from the owner of the property. These rules are set up for your protection.
You should contact The Contractor State License Board, they are willing to help you.