I want to remodel it and add two apartments in usable space inside, as well as remodel an apartment I already have to use as an Air bnb (since another apartment in this building is doing so well as one).

It's being replaced by a Benjamin .22 spring piston air rifle. 

I’ve never personally heard of concrete bags down the sewer line or chocolate sauce in the air vents level sabotage before but I’m sure it’s happened.

In NC, the following definition applies to common elements:"Common elements" means any real estate within a planned community owned or leased by the association, other than a lot.So  unless owned by the association and leased, then no they may not.Earlier in the by-laws, limited common elements are defined:"All decks, patios and balconies, utilities within each unit, furnaces and any air conditioning, appliances, unit windows and doors, unit floor coverings, all interior sheetrock and wall coverings, shall be deemed limited common elements."

And while I think that gives a lot of downward pressure to keep things cheap.

Outside of some electrical concerns the house was very structurally sound and the plumbing seemed to be fine, except of some water pressure issues.

We got a duplex essentially 0 down, we offered $5k down owner financing, bought over market value (full asking price), cash advanced a credit card to pay for the down and closing costs, cash flowed every month and eventually raised the rents (to increase the value of the property) and sold it, making around $70k after cashflow and profit selling in a few years - essentially we created money out of thin air.

@Cameron Davis usually you are looking at a horizontal crack spanning the entire width of the wall as a result of the outside pressure.

I started a painting business 5 yrs ago, scad painting and Preservation, looking to for new clients in the area, tired of working for the middle man, looking to work directly with investors, I can provide roofers, plumbers, drywallers, flooring, pressure washing and the painting for a competitive price, I'm a small business, not too fancy yet, but my work is grade A

Poor drainage can be solved easily, but hydrostatic pressure is a much bigger deal.