You'll get a feel for the age of the neighborhoods, the vitality of the commercial buildings, the ease of location, the closeness to jobs.The markets you're describing are more linear, and usually have lower capital appreciation.

Be careful not to place your identity in your age/success in RE.

The rules are designed to prevent related parties from engaging in exchanges that shift high basis property for low basis property, followed by a sale of the low basis property, effectively "cashing out" without recognizing gain.If you sell a property to a related party as part of a 1031 exchange, both you and the related party must hold the exchanged properties for at least two years following the exchange.

The biggest factors, from what I can tell, are age and rebuild cost. 

I started at age 20, dead broke with no experience but hungry with lots of time on my hands. 

They knew a dog lived there when they rented it and they rented anyway, knowing they had allergies and chronic asthma they rented a home with carpet. 

Relatively small amounts of interest income ($1600+ per year) is the highest taxed form of income I have found if you have kids at home.After earning a few grand in interest, It takes away my child tax credits and gives me an effective tax rate of 70%.   

@Zach Howard there is no agreed upon Classification in the 1-4 unit market.We've done our best to logically create a system for our market, mostly based upon relative sale prices, but also using crime rates, rents, occupant income and a few other variables. 

The house was spacious enough for her, but not for accommodating other relatives who might want to live with her.

I think another factor here in determining whether its a good investment is your age and your goals.