Legal Question in Real Estate Law in California

Hard to say without reading the lease whether the landlord will be successful in the unlawful detainer lawsuit. Certainly you can be served with it, the only question is whether they would win. If in fact you had a 10 day grace period, the 3 day notice would be invalid and, therefore, so would the UD lawsuit. But you would have to have your lawyer file appropriate responsive papers raising the grace period as a defense. If you are served with a UD lawsuit you will have only 5 days to respond, so better start calling lawyers now. If you attempt to act as your own lawyer you'll be living in the street. I have often beaten back UD lawsuits based on invalid 3 day notices. I also often get calls from people with 1 day left to respond. I suggest you NOT wait until it's too late for a lawyer to draw up the responding papers.

It depends on the nature of the grace period. If the terms of the lease are that the rent is due the 1st and past due after the 10th, then it would not be legal to give a 3-day notice before the rent is past due. If, however, it says the rent is due the 1st but no late charges acrue until the 11th, then you are still past due on the 2nd and the notice would be valid, as would service of a UD complaint on the 5th.