As noted, it keeps capital available to replace the HVAC, when it goes out in your first month of ownership, or the roof starts leaking and you are chasing an unknown source to the tune of thousands of dollars.  

By installing our own, we remove the wear and tear and damage the tenants do by moving W/Ds in and out and hooking them up wrong (which is common) and using cheap components that cause leaks and destroy floors and walls.

After the tenant moved in the repair calls starting coming in 9 times in 12 months - backdoor was stuck again (that was part of minor repairs), heat went out, AC not cooling, kitchen sink leaking,  etc.

She had issues with her kitchen faucet leaking.

Personally, I'm currently using Hospitable, which can automate a lot of the communications (even detecting and responding to a lot of questions).

Not to mention, solar panels can also be a cause of roof leaks and require regular cleaning to maintain some level of efficiency which is not great to start with while also getting worse over time.

There are far fewer opportunities for leaks to develop in the drain plumbing under the sink when there are less than half the amount of joints within the plumbing.  

The leaks are visible from the inside of the roofline inside the attic, if there is one.

If they are in an upstairs apartment and leak, the damage can extend to the downstairs unit.

This July, the tenant complained about a leak that managed to seep through the walls and onto the floor from the attic.