Definitely get landlord accounts if you can to prevent service from being shut off between tenants.

Are you replacing both the condenser and air handler for $2,800. 

The amount of dust and fibers and just plain YUK that's being kicked into the air is annoying, particularly as I'm finding it in my fresh paint now and it's really pissing me off.  

If you know the right people (our realtor gets a discount) they only cost about $400-$500 a year and will come out and fix any appliance for about $75-$100 fee but will not replace them. we have used them once just because it was cheaper than paying a contractor to do it when our air handler went out.

The complexity of the question should prevent you from doing it.Each deposit needs it's own account.

Vacancy rates during the summer months can cause a bit of an issue with cashflow, but I know of one person in Virginia who uses the house as an Air BNB during the summer months which could help a bit.

If a property or your business is set up for short term rentals like Air BnB, your pool of investors are going to be limited. 

The price does not include any exterior work to prevent water from coming in.

If it was mishandling of a firearm, that MIGHT have prevented it if the tenets cared once again. 

Currently, there is only 1 huge old gas hot water furnace that services the whole house and 2 hot water boilers, 1 services the basement and first floor and the other one services the top floor.I have been quoted $18k for a complete forced air, central air system for the 3 units.