Legal Question in Real Estate Law in California

First, I can't think of any law or process whereby a husband can eject the wife's guest from the marital dwelling, irrespective of whose name is on the title. Maybe if your mother were growing marijuana or something. Ordinarily, no. Ask him to write down the code section he would rely upon, then re-ask that part of your question.

Neither spouse may be excluded from the other's dwelling. Family Code section 753.

As to ownership of the house, if you owned it outright upon marrying, it remains your separate property to and including divorce or death, except and unless (a) you make a gift or other transfer, in writing, of an interest to your husband; or (b) to the extent his funds, or community funds, are used to make additions and betterments or to reduce the principal on a mortgage.

Here, you say you've been paying for it. This raises a likelihood that the money you're using is community property, which includes your paychecks from employment while married. If, for example, your mother were giving you the mortgage money, that would be different, but if you are making payments from your wages or salary, or from a commingled bank account, the marital community is gradually acquiring a small interest in the house. For a further explanation, look up "pro tanto interest" and "Marsden Moore formula" on Google or ask a family law attorney on LawGuru or in your community. I believe a pro tanto interest is reimbursible upon divorce.

Mr. Whipple is correct on both counts. To clarify the divorce part of your question: the "Moore-Marsden" rule basically says that when community funds are used to increase the value of separate property, it does not transmute the property to community property, nor create an ownership interest belonging to the community, but upon divorce the community funds must be returned to the community "pot" in the property distribution. Only community funds that increase the net value are counted. So if you make a mortgage payment with community funds on your separate property house, the portion of the payment that goes to principal counts, but the interest does not. Similarly if you build an addition that counts, but if you pay a weekly gardener it does not. As you can imagine, there is plenty of room to fight over what are expenses and what are improvements, but most commonly they are resolved along the lines of what the IRS would say is an expense versus what would have to be depreciated, if it was a business property.