@Adam Sharp I use this one (don’t think you have PA down south though) https://www.princessauto.com/en/detail/2-3-mm-hvlp-gravity-feed-paint-spray-gun/A-p8528523e;jsessionid=AZwJYRn8QUNQro43udVtW2b9.pal-prod-com3Wide variety of gun quality and not all expensive ones are great, same as not all cheap ones are crappy (but usually cheap ones are).

Inside you have old plumbing systems, knob and tube electric, old boilers and radiators or gravity fed furnaces.

This appears to be gravity-fed hot-water heat, so that would lead me to believe there is just one heating system, which you'll be paying for.Your analysis shows both units being rented out.

They are trusting you to protect and build their future and if you accept their money, you need to understand the gravity and importance of that. 

Im not saying it doesnt happen but Its not common practice to use a directional boring machine on a gravity sewer.

It uses gravity to level out so flat surfaces are best.

With gas (or propane) you need a chimney for gravity vent units, that means you now have to properly maintain the chimney and possibly install a liner, repair masonry, etc.

Wow that house even has broken gravity!

One can only hope so, but the markets in many parts of Canada have been defying gravity - and mathematics - for so long that people now believe it to be normal.It certainly appears to have peaked for us ... we have not bought anything in over a year now and are 0.5 for 8 on 12+ unit properties in our area {the 0.5 reflects an interim position we have taken in a property with another investor}.

The joists sit on the sill and gravity does the rest but in order to jack the house you need to brace with temp beams and jack as far out on the joists as possible.