It all seems so clean and simple...so why doesn't anyone else do it? 

I think with the lease and local laws I can find a easily justifiable way to pin this to both their backs, but I'll trade my right to leverage terms for a clean break and ability to move on.  

Clean the yard at your expense.

In light of that $650 seems reasonable if your units are updated, clean and frankly somewhere you'd live without thinking twice about it. 

Brokers like things to be clean and easy (this is not a slight to brokers at all) without much potential liability.

@Jessica Mendez please see https://www.cdc.gov/mold/Also, one of the best and non-caustic/non-toxic ways to remediate mold is commercial grade Hydrogen Peroxide...safe and penetrating...https://www.reference.com/home-garden/hydrogen-per...http://greenopedia.com/clean-mold-without-bleach/

They seemed ideal, they paid rent early and kept the place reasonably clean. 

Is it clean title, no liens or extra backed taxes?

It's my first one but my goal is the same, single, 30, no kids, no pets, want to rehab distressed or vacant areas around Bangor to help clean up neighborhoods and provide safe clean places for people.

Then the slate is wiped clean and you can start again