The average tenant in Trenton City is going to have a sub 650 credit score, a lower wage or unstable job, etc.

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:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+, zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680, some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

I have $500k in cash to invest as well as a credit score between 750-800. 

Pleasant but could never score any lots there that made sense.

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

My advice is to pull your own credit scores so you know what your own FICO is, and ask the local (to the property) credit unions. 

I put a link from Rentredi if anyone is interested to look.My screening criteria is 3x monthly income, Credit Score >600, no Felonies, and I have really be on the fence pets or no pets depending on size etc I need help with the tenant selection1.

I've been educating myself on real estate for the past 3ish weeks or so but I have about 10k worth of credit card debt should I try and pay it all off so I can get my credit score up and have better approval odds for my first investment loan (I would be using my VA loan).

Yeah, but then you also said "And to give you some context on how "rich" the PMs are getting, in case you are wondering for your own PM business, the margins in this business are incredibly slim" which is probably the most untrue statement.