Their fill hose sprung a leak or something and hundreds of gallons of water poured into the apartment below them.

How old is roof, mechanicals, FFE? 

Milwaukee inventory has just been so low, that even very distressed properties sell to first-time home buyers without a significant discount, so in the end it's cheaper for me to buy properties that already have a new roof, windows, kitchen, HVAC etc

If you buy a house you get a full inspection and check all its points, termites, roof, etc.

I think the A frame idea works great for this setting, but some have said the A frame style steeper peaked roof works better. https://www.instagram.com/redtail_cabins_adu/

After a few too many midnight leak repairs, she wanted to offload it but didn’t want a big tax hit.

It's an A-framed garage with shingles roof, gutters, windows, and a 32" exterior door (in addition to a 16' operating face door). 

It's a 4 bedroom SFH for $325k, built in 1990 and it's got many upgrades including a 2024 roof.

I'm thinking that repairing the plumbing leaks and getting the soil dried out could be a permanent solution.   

The worst experience we've had was with a flat roofer (very common roof type in Chicago) we finally wrapped up, after waiting almost two years for them to finish/fix something.