That’s not taking anything out for tax, insurance, repairs, PM, vacancy like it should.

Then guess what, the heater broke down again today, day 2 since notice, one week after the repair. 

Very often they won't include repairs or CAPEX.

they once told me that it just meant it was not habitable and if it was not repaired soon the city may require it to be demolished. 

Haven't used a property manager, however all repair and maintenance expense has been included.

I currently have Duplex under contract that will need significant repairs and would like to start geeting in touch with some contractors.

Regardless of renting or selling, I'm looking at spending around $2,000 for smaller repairs which include paint, replacing carpet in the basement, and replacing a bathroom vanity. 

Smart you have a FT and PT job- I think you should essentially dive in.. but not make a "bad purchase" , since you can't win on the sidelines You absolutely want to have reserves when you invest, it would not be smart to have limited capital since if you have a major repair, you will be in trouble. 

A reputable solar company will either not charge, or will charge a nominal amount to lift and replace the system to allow the roof to be repaired/replaced.

I want to get an idea of repairs on leaking snap ties.