Initially, our plan was to fix the drywall leaks, clean out the property, and relist it for a small profit.

@Chris Seveney I remember when cupcakes shops were popping up everywhere and were a big thing.Then, poof, most of them were gone!

I know they are crazy guest friendly but this seems over the top.Guest didn't deny it....responded with "I payed the cleaning fee, why would I clean up?"

bottom line - you can't use a square foot estimate... you need a bottoms up estimate as @Samuel Eddinger alluded to.  

Nothing worse than walking up the front of the house and having a broken up concrete walkway.

I would assume the purchase contract has a clause that states title is clean and there no encroachments.

With the exception of 1 bedroom units, you basically have 2 options:-Oversized/commercial machines (potentially multiple sets)-Off site cleaning with clean spares on siteThe latter is almost always the most efficient and basically what hotels do at scale.

Initially, our plan was to fix the drywall leaks, clean out the property, and relist it for a small profit.

Initially, our plan was to fix the drywall leaks, clean out the property, and relist it for a small profit.

If the house has a septic system, especially if it's an older one, it's worth the investment to have a septic inspection done.This concern is particularly relevant for those planning to buy and hold the property rather than simply fix and sell it.