Having learned a lot with the first purchase, I'll be doing the rehab on the next rental differently...more conservatively...more sweat equity on the simpler things (demo, painting, kitchen installs, etc.). 

when doing the demo shut off everything. long time ago they used gas for light fixtures.

File place has a demo version, looks like its a product being sold online.

You don't say how much demo has to be done, but you can think about it the same way you would a new build.  1.

For demos it saves so much compared to dumpsters .

I want experience in framing, drywall, cabinet install, tiling, demo, etc.

I don't agree with your argument …   having had many a house razed by the city and then get a bill for it.. just had one done in Indy. but that's because we did not get to it in time to rehab  we were going to demo it anyway.  

I recently did a demo with them, but it all seems too good to be true.

Ask for a bid broken down by room in detail ie: demo costs? 

It is "probably" not structural if it was poured after the walls with no connection to them.If it's just to make a floor, you can demo it and pour a new pad (4" thick).