Who do you use for background checks?

I have a relative that’s looking to rent out his spare bedroom and wants to do a criminal/tenancy background check on a possible tenant. Her asked for my help and I realized I have no idea what is a reputable service to do this.

There are so many fake-looking sites filled with artificially long wait times while they “generate” a report and I can’t find a single service that gives pricing for a one-off check.

This is happening in California.

I am sure I’m ignorant about all of this, so please educate me!