Possible main drain pipe replacement and new natural gas heater needed. 

If you have not covered up the subfloor yet, stop in to your local pet store and look for "Natures Miracle" it is an enzyme to eliminate the urine.  

This would of course require 3 base things:  1) efficient utilities- a natural gas hookup in this case, 2) a well insulated house (sometimes challenging in the multi units in New England), and 3) implementation of a landlord thermostat to control the heat and regulate it to a range 65- 71. 

Underwriting for a living, naturally the idea of investing in real estate appeals to me.

1) there are so many built in transaction management systems online and for the high performing agent hiring a TC is becoming 2nd nature (most offices mandate and most escrows now include them for free in transactions) Dropbox and cloud drives seem to do the job for disclosures and Zip forms seems to create an online heaven for digital document signing and storage.

Learn to purchase properties subject-to and keep adequate cash reserves to service capex issues.  

cost to hook-up utilities such as sewer, water, natural gas5.  

I have adequate cash for a 20% down payment if necessary but prefer not to get killed by an investment-type loan. 

With cyclical nature of market, should focus of investor be on different kind of property at different phases?

If you dislike your current agent and don't intend to work with them any more, then it's a moot point.If it were an off-market deal agents can often understand the nature of that, but when I have had clients go through the listing agent in order to save money on the commission (which almost always is shown to be a non-reality once you see the settlement statement), it has clarified to me that they don't need OR want me to labor for their best interests.