There is asbestos insulation, and rotten sills on both the garage and the main house, and electrical problems (short in the bathroom, no grounds, and not enough AMPS for the house).

And my rentals are q-tip clean...something everyone appreciates.

The cost to bring both gas and electric to the property ended up costing about $12,000 more than anticipated.

You will also want to understand common area maintenance, especially if you are targeting 3 units or more (lawn care, snow removal, cleaning and upkeep of common areas, etc) and understand the parking situation.

Can anyone recommend a reliable HVAC company to service (check out system) and possibly do duct cleaning?

The listing and marketing is fairly straightforward and they include ways in which you can directly divert fees, cleaning fee, directly to the contractors responsible for those operations. 

.- Electrical AMP needs to be updated for all lots.- Trash utility included as part of property tax payment.- Market lot rent: $410 - $460.  

I put a new roof on it, cleaned it up and resurfaced the driveway.

Odds are pretty good that she left and you can simply clean the place and move on.

The key building systems are the plumbing system, electrical system, HVAC system, elevator system, escalator system, fire protection and alarm system, gas distribution system, and the security system.