Remember if your rental is creating a profit in excess of depreciation, paying some more income tax is a good problem.

There are two possibilities going on here and you didn't specify which one you're dealing with. 1: they work with a company that installs the panels, gives them free solar energy, and then sells the excess.

You need to be honest with yourself about your risk appetite and your ability/resources.  1.2k is not enough, but is 1.5k? 

Essentially take all the excess cashflow from your investments and put all of it towards one mortgage until it is paid off. 

Cons: The initial paperwork which I thought was a bit excessive. 

During the great recession lenders just didn't have an appetite for commercial. 

Losses due to excessive wear-and-tear?

@Bernie Indig I understand that eventually you want to connect with people with experience, but what you've just said is that you have excess funds but no understanding of any areas around you.

An asset can still be excessively overpriced in a high cap rate market.

Even with $6,000 cash flow, a big tenant turn (I see an average tenant turn ranging from $1,000-$3,000 for owner responsibility,) excessive holding costs (high mortgage, lawn care, utilities, taxes, insurance, etc.,) and/or extended vacancies (tenant moves in a bad time of year, turning the unit is slow, etc.) will wipe out your reserves.