There was only a verbal agreement to do the homeowners landscaping project. I completed the 3 month project and supplied all materials and labor as well. It cost me roughly 6500.00 out of pocket and that does not include time and labor. The homeowner was to provide me a room in his home in exchange for the work but has now decided to rent to a new roommate for 350.00 a month. Says I'll have to take him to court if I want anything out of him. Any advice? Steps to take in California?

No, oral arguments are enforceable. Take it to small claims. In the future though, always use written estimates and get costs paid up front.

Take him to court, but in the future if it is any sum of money at all, do it in writing.

But verbal agreements are enforceable