A close family member brought to my attention that the risk of buying an old home like this is having plumbing, sewage, and electrical issues because during the home inspection you cannot see these things since the plumbing is underground and the electrical is behind the walls.. 

Market rent doesn't go UP or DOWN that fast; you'll find 9/10 properties don't pencil out and you don't have to waste anybody's time (extremely important to agents).

What did it do to the walls?

I wasted most of my money on things and didn't save for my future. 

And also what would you have them sign so your not wasting your time?

The old 6 gallon toilets would overflow if there was a clog and they wasted water.Like most things, there are two sides to this debate.

You definitely give up on a few things - complete privacy (multi-families are old, with thin walls and creaky floors), sharing a backyard (we never felt comfortable having friends over and having too many beers on weekends or holidays), and we were always in landlord mode mentally (let us know if you need anything!

I've only ever used for bathroom walls/floors before tiling or creating an outdoor bbq before faux bricking, etc.

However, for small MF and SF, there's no need to waste your time visiting every single property you get under contract during due diligence.

Replaced picture window with 15 foot slider, built a deck, added a laundry room, installed new hardwood floors, replaced the walls, ceiling, moved windows and doors.