A friend and I co-own a CA rental property. If I bought him out and he provided me a quit claim deed, would a property tax reassessment occur?

Yes, California Revenue and Taxation Code §61(f) makes any transfer of a tenancy-in-common interest a change of ownership for real property tax assessment purposes, unless it is covered by any of the exemptions in §62 and §63. The facts you have provided do not suggest any such exception, such as a divorce, inheritance, or transfer from a parent to a child. If you appreciate this free advice, please remember to refer me to any friends or acquaintances who need a lawyer. Referrals are still our best source of new business. Do you have a revocable living trust to protect your heirs against probate? Probate takes forever, is expensive, and is annoying. Do your family a favor. Set up a trust, and put all your property, especially any real property, into the trust. Since it is revocable, you can change it, add to it, take property out of it, or even cancel it completely, at any time. We set up such trusts, provide a pour-over will as a back-up for any property that does not make it into the trust, provide you with blank durable powers of attorney for health care and financial decisions, in case you become incapable of making such decisions while still alive, and convey one piece of real property to the trust, usually the family home, for $1500.00. If you would like to hire me to do this, let me know, and I'll send you a list of the information I need. Dana Sack