The one thing I will say that is finicky is the electric on-demand hot water heater: it doesn't like it the hard water from our well so we had to upgrade our water softener to the best one available, and it also doesn't like it when my wife runs the dishwasher, clothes washer, and tries to take two long hot showers at the same time.

If I were you, I would analyze the best I could and probably do the upgrades, this would increase cashflow and ARV, then pull out some cash in a HELOC or Refi to while saving $ to buy the next house hack!

Part of what prompted this is to separate electric, I'll have to pay quite a bit more than the required electrical work of upgrading the service.

Upgrade interiors to Class A finishes.

Upgrade interiors to market style.

Made upgrades to the home based on inspection issues with electrical, wood rot etc.

Steady cash flow, good tenants, homes will need to be rehabbed in a couple of years to upgrade finishes and rents

If it makes sense to sell and upgrade, you should almost certainly consider a 1031 exchange. 

I agree I think it gives more flexibility and options for the real estate, including cushions and providing upgrades for tenants. 

We originally planned to do leases only but pivoted to STR to maintain access to the older part of the property that will need gradual upgrades we aren’t immediately ready to fund.