I'm looking at replacing the gas heater with a newer Rinnai heater for the safety concern of using half a dozen space heaters.

(If you're not living on the edge, then you're taking up too much space)  

This means your available reaction time is also cut down.You should be able to see and control (with proper market analysis), the next 4 - 5 years...in 1 -2 year increments.

Does the bank cut me a check for hard cash to repeat? 

One day its the fridge, next AC, next bathroom fixtures, unless they are paying top dollars and you can afford to upgrade their life, its better not to fix it unless it is a safety issue or broken (and sometimes tenets purposely break it because they want a new one). 

This cuts the margins for fix and flippers really thin.

The decision isn't so clear cut, however, and strategizing is key in this situation.Another thing that came into play is the possibility to defer payroll taxes for a while, even if you got the PPP.

The city was probably sick of cutting the grass.

I would do nothing beforehand except obvious safety concerns-broken windows and loose or missing rails.

However, if you plan is to fully stabilize the park and refinance, 3 years will be cutting it close.