One realtor told me I could rent it for $2,000 a month, but I just don't see that based on comps in the area.The other factor is, I have a good income, and thinking through the hassle of renting to MAYBE make $100-200 a month doesn't seem worth it.

I have contacts in my investing group who are connected to manufacturers of modular homes - not "manufactured" (trailers), modular: homes are stick-built in pieces in a factory, the pieces are shipped to the home site on flat bed trucks and assembled onto the foundation.

A huge factor is the neighborhood in Philly.

I realize that as the leases roll over I can change the terms so that the tenant pays for the water, but am wondering how high the risk factor is in the meantime.

The other factor is, are you hiring a general contractor or are you the GC?

In your example it seems as though they couldn't care less how the money is invested so guess that isn't a factor.  I

The other factor is this  - If a contractor bids too low, then realizes in the middle of the project that he won't make any money, then you are working with a contractor that either is not a happy contractor, or they have to do other jobs to make ends meet on yours, maybe they even misappropriate funds.  

And the state law already provides that in both Upset and Judicial Tax Sales, the Realty Transfer Tax is based on the assessed value, no matter how low the actual purchase price might be.In one case I personally witnessed, an old abandoned factory building was sold at Judicial Tax Sale. 

I have heard that though most things are taken care of as you stated the biggest uncontrollable factor is the HOA.

It is an industrial building used by a plastic factory in LA, CA.