- Resurfaced deck with synthetic boards, replaced old carpet with either laminate or sanded the hardwood underneath, painted rooms, replaced old light fixtures / ceiling fans with modern ones, updated interior door knobs,  finished the basement because it is dry, installed recessed lighting in many rooms, upgraded electrical panel to 150A. 

The people I know who would be qualified to evaluate it might buy it out from underneath you if its a good deal, lol. 

Delivers it to the tenant, and apparently does some cursory check and informs my tenant that there is no grounding underneath the sink, and so the dishwasher cannot be installed.

Is the soil unstable, are the drainage issues, etc. check with the neighbors to see if they are also having settling, foundation issues.

A good master plumber can re-route the lines and do all the work from outside/underneath the property.

One thing that stood out to me in the presentation was he stated multi family owners could turn underneath garage parking into ADU's so I am sure your Triplex lot would qualify in SLA.  

@Mitchell Rusten you will need an engineer to conduct a soil test. 

Some places do allow to put a septic tank in front of the septic if the soil percolates well but I wouldn't count on it. 

Coolest thing I ever saw for a bath is a teak floor that has a drain system underneath - lol - but that's not exactly anything most of us will ever consider, unless we're doing the highest-end stuff and want to get super fancy.

There is a chance you can support it from underneath with shims to place pressure from the bottom.