My wife and I are in the same boat right now, dabbling at listings or off market whole sale "deals", or paying down RE debt.

The QBO class tracking feature, found in the more expensive Plus and Advanced versions, is used by many investors.

great question cant wait for feedback currently in the same boat 

 I think changing from a “don’t rock the boat, keep rents stable for ‘good tenants’ ” mindset to a Vacancies aren’t the worst thing on the planet mindset as paid off in spades.

You can also take courses/classes on this subject...but it will take you a while to know and understand what the right process is.Again, there are lots of details that we cannot see here.  

It cost about $3200 (they will send you a discount code if you look at it a few times) and had 6 classes all 2 weeks long.

Those states have "income source" as a protected class and as far as I know are only the west coast (CA, OR, WA) and the new england area (MA, CT, VT, NJ ect) Account Closed  In most states you are not required to accept Sec 8, and as such if you choose not to you could deny processing an applicant that is using a voucher.

I've been looking at investing in small, multifamily property, fix and flip (or hold), storage units, truck/rv/boat storage lots, etc.

Like Detroit, Saint Louis is incredibly "block by block" where one area is experiencing gentrification or at least just a stable middle class feel and that might only be 100 yards away from a street that will be un rentable, un managemeable, and honestly a bad place to get out of your car.  

I would guess you are thinking of a 60-80 foot boat which ain't gonna be cheap!