help deciphering some numbers

[Eric Furst]

I'm looking to move from playing the market to real estate investing, but trying to start out in a low risk/low reward property in order to learn the ropes. I've been looking mostly on roofstock for my first buy. In researching some of the communities with available properties I've come across a number of statistics. I was hoping some of the experienced investors here could help me decipher some of the numbers.

Vacancy rates, crime rates and the like seem pretty obvious to me; the lower the better. Some other figures are a bit more confusing though.

1- Rental rates- Do these concern you as an investor? If only 15-20% of the population rents is that a problem or can that actually be a positive as it develops a "community" and keeps the few renters around longer. 

2- Is the population growth important? If one region hasn't grown much over the past 10-20 years is that an indication of stagnation, or the sign of a more mature community? And, on the flip side, is extreme population growth sometimes a red flag?

3- On the vacancy rates, while obviously the lower the better, presumably there are a number of houses that are vacant because they aren't rent-able. Is there a way to calculate the percentage of properties searching unsuccessfully for a renter?    

4- Lastly, in your experience, how much does past home appreciation in a region portend future growth?