Heating is Electric by old radiator or fireplace with natural gas, and A/C window units though out the house.

I’m finding sites like Rentler or Azibo only allow landlords to set a fixed amount each month for rent and I really don’t want to be charging my tenants rent and utilities on a different platform.

Airbnb is just a platform to list a STR.I have found the best vacation rentals I have stayed in where self managed.

I walked the property and its in good overall condition. windows, trim, furnaces, floors, roof…all in good condition.

I think rents are on an unsustainable trajectory but I do see a window of another 6-9 months where before the price of land gets bid up beyond a point that it makes sense for a build to rent play. 

What is another good permanent option to get ac in these 2 units without using window units?

It has window units for air conditioning and base boards for heating.

I set my company up as a cloud brokerage, meaning that I don't have a Main St. office with the big plate glass window full of listings - but others may feel the need for that office space, with its $5,000/month overhead. 

Nicholas Dentice, investor and owner of Denco Windows, sells used appliances. 

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.