All of those people also get credit/background checks. 

CA taxes residents on worldwide income but may provide a credit for taxes paid to other states.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

Quote from @Divya Sosa: Hello,I had a unit up for rental (a townhome) and received an application from Zillow which showed that she has no criminal history and credit score was good as well.

Get knowledge, follow experienced people, and leverage wisely.My Take:If you have two houses, excellent credit, and motivation to build wealth, you can learn to manage your money responsibly.Use HELOC, credit cards, and business credit funding to leverage your cash and buy properties faster.

I’ve read quite a few posts about foreign investor financing but most seem to deal with non-citizen investors without US credit or personal tax filings.

I require a high credit score 680+ and two prior landlord references.

Do not forget to prepare the balance sheet, track distributions etc.

This is what we tell members:  These teams have a track record with us.

A proper vetting process - background, employment, credit, and reference checks - will weed out 99% of problem tenants.