In my opinion, one cannot assume that when ownership changes hands, customers will continue bringing their business to the same shop (especially commercial accounts). At least make sure that the existing commercial contracts do not have an opt out clause that can be triggered by ownership change (or any other change for that matter).
You have stated that you just want to be an investor, and (correct me if I am wrong) 100% owner (because you have "bought" the business). Your technician (previous owner?) becomes "labor" with no "skin in the game." Most CA smog test only centers do not employ more people than absolutely necessary. What I mean is, the technician(s) will also need to do the administrative paperwork on the back-end as well. And in CA, there is a sh!t-ton of administrative paperwork to do (not to mention the inevitable government "secret shoppers" -re: inspectors- that want to make sure your business is not "taking any shortcuts").
If you must buy a business in CA these days, then consider the prospect of a partnership with a current owner/technician. This type of agreement may allow you to limit your liability.
However, if I were to buy a business (any business), CA is the last place I would be considering due to the governmental framework and litigious nature that exists in (my home state of) CA.
A bit of background on me:
From approx. 18yrs - 24yrs of age, I helped mange janitorial supply stores. One small outfit in the suburbs of LA, and one larger outfit in Santa Barbara. Both of which had owners that left the day-to-day operations to their hourly employees because they were too old to do the work (getting their hands dirty or managing accounts). I experienced firsthand the nightmare of landing new and/or retaining existing commercial accounts (because they are almost always trying to deal with their own budget constraints).
From approx. 24yrs - 32yrs of age, I was a financial advisor (for a couple years) and a legal expert for a life insurance company. In both jobs (especially my 6 years as a legal expert), I advised attorneys, accountants, and financial advisors on the more complicated cases they had involving business continuation (should accident and/or death happen) and how to mitigate those risks using various trust and partnership agreements (funded with life insurance products of course). It really opened my eyes even more to how difficult all phases of business ownership are (all types of businesses, you name it). I saw a lot of small businesses in CA (that had a good business model) either close or move out of the state due to various law and tax changes made by the legislature.
Unfortunately, my opinion of CA legislature became so jaded that I decided to move out of CA (and the country) indefinitely. In my opinion, the biggest risk to you and your commercial account customers is "legislative risk" (re: the risk of legislature changing the laws/rules regarding taxes, administrative requirements, procedures, etc. at their leisure).
I really don't mean to come across as negative...just trying to be realistic (without knowing all of the details about your situation). wrx1456 gives some good points. If it was me, I would want to own/run a business that had less competition (more of a niche).
Thanks for enduring my post, and the best of luck to you.