This vary heavily town to town. 20% down is great if buying strictly as investment but if you have a way of owner occupying I would explore that route and apply the 20% down to increasing value of property and instead using low money down loan. 

Since you’re still figuring out where to invest, look for areas with strong rental demand, good schools, low crime, and potential for future growth.

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

You also get 100 free credits on sign up so great if you just need a smaller list done. 

I'm working with a company who owns a small, 19 unit, senior and low income apartment building.

To access your home equity without selling, you can explore options like a home equity loan, a line of credit (HELOC), or a cash-out refinance.

@James Tobin  yes FHA will be a very low downpayment option for you.

Or we gradually perform high-quality updates for a live-in flip, then roll the equity into a new home.Regarding rental income, we aim to boost income, lower our effective tax rate by generating more low tax-drag income with rental income (since there’s not much we can do to lower out W2 tax bills) and have retirement cash flow.To compare the financial impact over 10-20 years, we want to analyze renting versus flipping.

(Churches are surprisingly low value structures.

Long wait but I got a lot of upgrades for a very low price.