For the rentals, you can get a low interest SBA loan of around 4% (no grants). 

In general if you're going to do conventional financing, you can put down as low as 15% on a single family or 25% on a multifamily.

With a HELOC, you have no extra expense (some HELOC has annual fees, but they are low - like $100 - $200 at most which is negligible) unless you actually pull the cash out.  

@John Trommelen there are lenders that will go as low as 15% down but you will have a higher rate.  

still good potential for families looking for a home to rent and prefer more privacy. depending on the home, area ,etc. maybe a better caliber renter and less turnover of you can find a long term renter. make certain to still do background checks and try to get them to maintain the lawn, etc. they should pay electric and heat but keep the water bill in your name but still try to bill them for it.

Your revenues seem very low at 53k/year. 

The issue was the boiler pressure, if there is not enough it is not able to heat the water consistently.Check your boiler (and perhaps under it) and take a look at the pressure gauge.

If they pay low rent then they could still be below average for sales but make a profit.

Is the demand just low at this point?

C = lower middle class housing, more multi-family mixed in but decent places, some crime but low-level stuff nothing dangerous or violent.