If it's just a matter of being able to troubleshoot the occasional modem problem, I'd take that risk any day. 

If you can troubleshoot all the problems from toilet flappers, to clear drains, and all moving parts cleaned and working well BEFORE the tenant moves in, it will reduce calls.

For me I can troubleshoot furnace issues but if I have a tech come in and tell me the repair will cost a couple hundred bucks I'm replacing an older furnace o a more efficient model every time. 

If the water hasn’t drained after the cleaning then you can trouble shoot a couple of other potential issues like a kinked drain hose (YouTube will have several videos) or call a technician.

As was posted above, I believe the most money is saved by troubleshooting problems rather than immediately calling in expensive professionals.  

It depends, if she is good, keeps the place clean and pays on time and hasn't been much troubleshoot.

I ask where they've seen the bed bugs so I can come and inspect and they claim that such a question is proof that I knew of the bed bugs...After going around the world with this guy to explain that this is a normal troubleshooting step, identify where they've seen them so I can come and look, he claims he only responded with logic and that I'm wrong....Then he sends me another email telling me I'm being volatile and defensive...Then this beacon of logic asks me at 10:00 PM what time in the morning the exterminator will be by.

He also didn't even tape it properly (still gaps), didn't press it down all the way (my friend did), and left pieces of insulation all over the floor.Handyman checked pipes under the kitchen sink to troubleshoot why dishwasher drainage floods the kitchen.  

Did you really expect the Plumber to come to the property and troubleshoot "for free?"

Wow, you've done a lot to troubleshoot it.