The property tax BASE rate is 1% of the sales price plus assessments, voted indebtedness, etc. A fair rule of thumb is an additional .25% of sales price for these. Therefore, figure 1.25% of your purchase price for the annual tax bill. San Gabriel does NOT have a Point of Sale inspection at this time (Pasadena and Monterey Park do)
A few nights ago, I was sitting in class at UCLA and listening to a class presentation from a representative from the Los Angeles County Office of the Assessor. Property taxes are paid through this county agency. You can go to their website and get all the information that you need. There is alot of information on the website. You can start by going to the general information link.