Otherwise you are just giving a deal to someone else.Another option is to partner with someone that can project manage for you.I do think that if something is just way to emotionally draining, it's totally fine to sell at a loss and walk away.

He said the old iron pipe had deteriorated and he would have to cut in to the wall to replace the drain pipe.

As for the septic that could cause unique proportys in a rental, if your tennent doesnt know better they could really mess it up flushing things that dont degrade or kill the bacteria in the system by dumping household chemicals down the drain. 

Which would not be ideal, but would be draining the 4% savings anyway, to just fill back up.same with spending on my hobbies, no saving up for that wheel set for my bike, just use HELOC. 

It is now towards the end of January and he’s only demolished the third floor bathroom, installed new water and drain lines, and put a sub floor down.

Obviously a French drain system would need to be installed outside.

I recently purchased a 6 unit that drained my savings so I'm hesitant to overleverage myself.

Horizontal metal drain pipes are plugged and don't drain,leak at worst times.

Aka change the grade   3) add French drain to divert water away from the home usually into a dry well. 4). 

For example a newer build will have copper or pex pipes, PVC drains, insulation, poured concrete basements or foundations (no block walls), and three-wire electrical.