I, for one, would never vote for a mayor that had no experience in public service. Being unpaid for your time shows that you are committed to public service, not just looking for a job.
Excellent suggestion. I can think of a person, right now, who started just that way. Began in small ways, working on local projects within the community, and then ran for a seat on her city council, later running, and being elected mayor.
She was appointed by the governor to served on a state commission where she make her mark fighting corruption. She was eventually elected governor of the state and, as of this writing, is seeking higher office.