Extension cords everywhere from an outlet they found on the apt roof.  

For electrical as long as you have enough outlets you'd be fine. 

Also, depending on your area, you may have to add more outlets to make it suitable for a bedroom and most garages are sloped slap on grade and are not sealed verywell to the elements.

You got your property back and back rented out.

There is a way to do it but once you find out let me know. 

It's not going to be a problem, ever.The only thing to be careful about when you find random PEX fixes in an older houses, usually in an exposed basement, is the chance that someone grounded power outlets to copper or steel water supply lines up on another floor in some random remodel way back when and these outlets lost all  grounding when the PEX went in.

I'll also start putting up ceiling fans and light fixtures, as well and replacing switches, outlets, and covers.We will hopefully have this one finished in about a month.

Or sell and cash out?

The wires connecting to the dead outlets do not have power.3.

@Jim Windgassen  Everything about making accommodations for a level two charger you state before "existing 240 V outlets" I would strike.