Those states could be nearby in your market area.  

How do you go about determining market rate?

No issues and tenants are renewing.That indicates tenants were paying below market rates.If the market rate for a 2-bed/1-bath apartment is $1,000 without utilities included, then he should adjust his rate to $1,100 because it includes $100 in utility cost.

I would consider them to be more of a consultancy than a turnkey provider, and as such I think they provide tremendous value.Of course I could do all the legwork from scratch - research markets and properties, find lenders, get home inspectors and insurance and property managers and so forth - but RTR has already done all that and has far more experience and knowledge than I do.

My son currently lives in the townhouse b/c he is going to school and works in the area.Since he is young and starting out in life, I would like for him to only cover the basic costs (taxes, HOA, utilities) just enough for me to break even (I believe that will put him slightly little lower than market rent rates). 

Focus on learning market trends, property valuation, and different investment strategies.

An existing duplex provides immediate rental income and proven market comparables, reducing risk.

@Annabelle Rozen  I believe the stability of the rental market within Allentown is rather robust. 

The rental market has slowed in recent months but expected in winter.

I am in Tampa Florida so the investment market is huge here for both as well.