Mine is basic ,clean affordable no frills housing. 

Make sure it explicitly explains the process for termination if you are unhappy with their services, but especially if they violate the terms of your agreement.3.

I think you can only do this at the end of the lease like you have but make it a clean end and cancel of one contract and start of a new one.disclaimer: Not a lawyer

The actual unit maintenance is virtually the same as a regular HVAC, mostly be sure filtration is clean. 

What is your system for making there is enough money in reserves to service your properties without having to stock pile cash? 

Can pay a flat fee listing service... 

One suggested signing up for their service plan ($20/month per apartment) which includes one annual boiler checkup prior to the winter to avoid issues like mine and small discount on regular plumbing services (50% off of service call charge of $95 and 10% off labor costs after).Is this something you guys would recommend?

Airbnb is an option for the hold period that you describe, but who will clean the bathroom and wash linens between visitors?

I am a Field Service Engineer, I repair/service Nuclear SPECT camera's.

The gas company employees are killing there business here.One thing you need to consider is if the house has enough power service to feed an electric hot water heater, you may have to upgrade that.