Knob and tube is a great wiring system until someone puts a nail in the wall and shorts the circuit.

For me the ability to deposit checks from my phone is a deal breaker.

Its important to be knowledgable, but not should be really the deal breaker. 

Another red flag is a criminal record, again that may or may not be a deal breaker but if they refuse a background check I would be worried.Good luck!

100 amps per unit is probably ok. 100 amps for the entire building is probably undersized but if you are not tripping breakers or blowing fuses then you might be ok.

They can also borrow my car when I’m flying so location is not necessarily a deal breaker.

So, he thinks each plug needs it’s own GFI device and circuit breaker on the panel.

A-36Gross Output: 208 MBHInstalled Radiation: Steam Sq. ft: 650 ; Water: 180.9 MBhFiring Rate per Hr. 2.00 GAL Also, do you think I need an electrician to figure out the panel situation or can I just individually trip circuits manually in each panel and confirm using a multimeter what each circuit is providing power to (if it’s a power receptacle)?

The outdated panel and breaker sooner than later. 

The current layout doesn't give you much room for a dishwasher, but considering it's just a 1/1 rental, it's a nice convenience to have but probably isn't a deal breaker for your tenant, who will likely be a single person or a couple with minimal dish load.