Making DD on remote area

[Shimshey R.]

Hi all BP members!

A little about myself;

I recently joined BP after trying to figure out how to generate passive income and eventually achieve financial independence. 

I live in a single family house which I recently bought. Still a good 79.99% mortgage on it. (As the recent sales of similar properties were higher than mines, I can likely get it appraised for 10-15k more than I paid for it) 

I have my 9-5 job that covers my bills, and I have a side business which brings in some money as well. 

I am looking to get started in rental properties, currently looking for SFR and eventually mutli family.

One of my struggles is that in the area where I live, the ROI I can earn on most For Sale properties is really low. Maybe 2-3 percent. Maybe. The only way to get a higher ROI would be to get foreclosures, which I can get up to 5%. Or through BRRRR or different strategies which I'm not interested at the moment.

Therefore I started to look at other areas, two of which caught my eyes. However, as I am still new to the game (or whatever it is), I have no idea ho to make my dd on the market. One of the houses I was looking at seems to have a great ROI, but I have no idea on how difficult it is to find a tenant, or the vacancy rate in that area. How can I figure that out? I'm a little concerned about reaching out to a property management company in that area, as I am afraid that they will make it look shinier than it is.

What is generally a good indicator of vacancy rates? That area I am looking has tons of houses for sale and tons for rent, all listed on Zillow. The census records shows a steady increase in population which I would think is a good indicator. But why are there so many listings on Zillow? 

More on this, if I can theoretically make 10% ROI, why wouldn't other, experienced investors buy those properties?

Basically, I'm confused on how to make my due diligence. Any help would be greatly appreciated.