Troubleshooting maintenance and dealing with contractors will also be very educational. 

Www.Appliancepartspros.com has great troubleshooting info too.

I always troubleshoot by phone before sending out a tech.  

There is some wisdom here in troubleshooting your online application and, heck, for this situation, try waiving the fee to get the application.

so...I just realized today that I had the hot water heater for the laundry room washing machine off.FOR LIKE TWO MONTHS.I was trouble shooting something and turned the breakers for the hot water heater off. 

I've never had a problem with timely scheduling and they've done full kitchen rewires for me all the way to improper ground troubleshooting in bedrooms.  

We are constantly going on calls where we have to troubleshoot error codes by calling the Tech Support lines that are only moderately helpful.Now, in about five years, I think tankless heaters will be pretty much everywhere and will have most of the kinks worked out.

Perhaps you could troubleshoot the problem over the phone with  tenant and have them fix it.  

Basically Hardware is the base of adding components, trouble shooting and also assembling a computer in a systemic way.

how did you troubleshoot?