In California -- a man moved into a property owned by his parents -- he and his wife had a lease in the beginning and paid rent erratically for several months over a year or two (2004 and 2005), then stopped. He was their 'financial advisor' and began doing their taxes a couple of years ago, when he changed the house on their tax returns from a rental property to a second home. He maintains in writing that he does not owe rent because the house is a second home, not a rental property. His parents want him out. How do they do this?

If they are not the legal owner you can call the police and have them removed from the property but you have to make arrangements for them to pick up there belongings but if they where renting I believe you need to serve them a eviction notice first