Legal Question in Real Estate Law in California

No you cannot serve a seller in a real estate transaction by serving the agent. You must have the seller themselves personally served by someone over 18 and not a party to the case, i.e., you can't do it. You can send them a letter at the property address, but it will not have any legal effect since they don't live or have their principal place of business there. I can't tell you from the information you provided whether to bring the agent/broker into the case or not, but it would be a bad idea not to do it all in one case if you have a case against them as well as the seller. Do not count on your "doe" pleading in that regard. Most lawyers don't even know how to properly plead and then use Doe defendants, and failure to do it right can get your case dismissed as to the parties you try to bring in as Doe's.

I agree with Mr. McCormick. You are already headed for the deep end by representing yourself, as you are bogged down with procedural issues like how to properly serve papers. If this case was important, you would hire a lawyer.

Your short-term problem of locating the defendant for purposes of service of process might be solved by hiring an experienced, professional process server. However, beyond that, you're going to need additional assistance at every step, including preparing a Case Management Statement (Judicial Council Form CM-110) for the CMC. If winning is important, retain an attorney.