Lisa: I see why you want to look it up yourself. If you go to the Riverside County Tax Assessor's website, all you have to do is type in the house number and Street name, and it will show you what the owner is paying in total property taxes, base and assessments, for that particular home. Here is the website: https://taxpayments.co.riverside.ca.us/Search.aspx
To determine what your taxes will be, you will perform you calculations based on the amount you will pay for the home. For instance a $250,000 home is multiplied by 1% which is the base tax rate in Riverside County. So a $250,000 home would have a base pay property tax amount of $2500.00.
Then when you click on the "Tax Info", tab a screen will display the "assessments for that subdivision". This is a "fixed amount", and is not based on the percentage of the property value.
Please note that "assessed value" is the value of the property when it was purchased. In our current market the assessed values are lower, of course because current values have declined.
(The Riverside County Tax Assessors office is updating them as homes are purchased or if homeowners request a re-assessment, however, if a bill is created based on the previous amount and has not been re-assessed at a lower amount then a correction needs to be made and they will issue a refund.)
Some subdivisions includes Trash Pickup in the property tax payment so at least you will not have to pay for trash pickup.
Just remember that every subdivision is a little different because when a CFD (Community Facilities District), is created it is unique for that subdivision.