These workers will be able to do some tasks on their own without the guidance of a licensed contractor, such as installing flooring, cabinets, countertops and fixtures, landscaping, texturing, painting and doing patching work or light repairs.

What type of roof is currently installed and what is the condition?

That would be for a licensed Electrician as @Tyler Amburgy mentioned, i would not recommend doing it as a DIY project, have a licensed electrician do it with all the proper inspections, helps to free you from liability should anything happen ( even though a lawyer will always find ways to get to you - no offense to any lawyers out there ) I am a contractor but i do not do any work on my rental properties or flips, i always hire local contractors in the area.

Any diy people work on hvac system?

If you DIY, it won't cost you 1,000's either...

Now as for DIY.

From across the room, a DIY job will look fine.  

Hello BiggerPockets  Community,I'm a contractor/consultant in Northern Virginia providing Home Automation (The Internet of Things - "Smart" devices), Security & AudioVideo design & installation services for both commercial and residential properties.

Many landlord will install separate utility meters in multis to off load this expense. 

I recently had a buyer interested in a home that had a very similar situation, but tied to the Solar system that was installed on the subject property.