You need boots on the ground for certain, as well as, zip code specific demographics on market cycles and trends in each area you explore, check with the Economic Development council locally aware of development in the area and future plans.  

Also learning about your demographic or your market can help guide the perfect tenant towards your rental.

So, I knew about the area, including demographics, the micro-economic driving forces, steadily increasing population growth, etc.

The demographics are very important and they should guide you to the right area. 

The numbers certainly sounds great on the surface, we always like to look at the population demographics and the unemployment rates in the area to ensure they are moving in the right direction for long term growth.

If college students are a demographic you would consider renting to, I would recommend making decisions to prepare your property for an increased level of wear and tear.

When you are buying in at a much lower basis, demographic shifts are more likely to move to you.

You can do target marketing where you choose certain houses by age demographics. 

Could it be that the seller sees a large nuisance of deferred maintenance or upcoming tax or demographic changes that will make the property complicated or less profitable to own?

What's the demographics of the condo?