"I had a tenant pour concrete down the drains. There was no repair possible. It was literally more cost-effective to demolish, salvage what we could and rebuild. It even got into the septic system and we had to settle with the city for damaging their infrastructure. Biggest nightmare ever. We sued the former tenants, but when you're suing a scumbag, best case scenario, you might get a 1990 Toyota Tercel.
Tenants are pretty decent as a whole, but if you have to evict, it's worth it to just offer them a couple hundred dollars cash to move out while you're there and can watch the whole process."