A buyers inspection is basically this
You find a car. Take it to a Volvo shop, I would recommend a Volvo specific dealer cause they 1. They know what they are looking for and 2. The check list for the inspection is going to be more layed out/more in-depth than a local lube shop.
The mechanic won't come with you to see the car, so basically your first inspection of the car is going to be you alone. This will be the step of weeding out POS cars with bad paint and not taken care of interiors. Go on a test drive, and see if there are any noises/vibrations/ect that are obvious to find, you don't have to make sure the cars perfect, just that an overall observation, the dealer will test drive it on the buyers inspection (or request them to) so they will be able to find nothing that you miss
As for finding a dealer, there is a section on the main forum page of Volvospeed about vendor/shop reviews scroll through it and see if you find any place local to you. If there isn't, I'd start a thread/topic requesting if any So-cal people know of a good dealer. Secondly call around for prices for the inspections itself, usually there will be two prices, one for just an overall inspection and one for an inspection including compression testing the motor, id obviously go for the full inspection. So id probably go and look at a couple of cars and take the best one you looked at to go insect it, no need to have them all inspected. Also Judging a repair shop from online reviews on yelp or google will not always be the best advice, cause in my experience only people who like to complain write reviews giving shops a bad name, that being said you can tell a lot by the shop of how willing they are to helping you over the phone
With s70's all being around the same price, don't settle on the first one you see, unless you think it's perfect. Paying $5k for a S70 with bad paint but under 100k miles shouldn't happen, you'll find a nice car, might. Take time but you'll find one.
I was just in San Clemente last week. I wish the roads in redondo were at least kind of close to the roads down there, it's gonna take some getting use to haha