Use this website as a great starting point for what areas to invest in.

@Henry Perez  Things like websites, bios and marketing materials help on credibility as well as your LinkedIn and Facebook profiles. 

The state website can also be very informative. 

Here's a https://www.irs.gov/businesses/cost-segregation-audit-technique-guide-chapter-4-principal-elements-of-a-quality-cost-segregation-study-and-report to the IRS website noting specific items that are included in the cost segregation study report. hmm, that website is a 404 error.  

The process for commercial properties is basically the same as residential properties, so it takes work.Again, echoing Dominic, a good investment is a good investment, whether you spent 8 months courting an owner to get them to sell to you, or whether it is on CBRE/Cushman/Marcus/Loopnet or any other brokerage website.  

Some ways to find that person is local Real Estate Investor Facebook groups, local Real Estate Investor Associations, Realtors who list multiple properties for other investors, Bigger Pockets website's forum, and local property managers.You will also want to try to get on the buyer's list for local real estate wholesalers.To Your Success!

Would that be, for example, if the PM says, "I manage a duplex for John Smith in Turlock," then I call John as a reference, ask John a few questions, and then ask John the address of his duplex so I can later look it up on the county website and verify if he is the owner?

I can send a million articles, but i encourage you to go to maricopa.gov in addition to the city websites where you will see all the development going on here at a micro level. 

I would recommend you start your search on the NARPM website.

If you go to the property appraiser's website, you can probably  look at the year over year change in the taxable value of the property.