You need to look over the financials, the budget, and the reserve study to understand the financial health. $125 sounds about right or possibly low. 

The answer to your question depends on the economics...

Less taxes and more economic stimulus, is a win-win in my book.The only question now is did the read my letter or did he heard my Bigger Pockets Podcast #82?

And some strategies work better in a specific location or at a specific point in the economic cycle.Start as soon as you can.

Wonderful news about your son's health. 

When you look at the amount of money they spend on these projects, you often wonder how they make economic sense. 

Framing also looks in good shape with solid footings under beams.My assumption here is, given the scope of the  work to fix, this will require the town's sewer dept and/or health dept to get involved.I'm trying to decide if I should wait out the seller to fix and keep going through with closing or just take back my earnest money and keep looking for something less problematic from a sewage/sewer perspective.

WE are not here to discuss economic inequality, social inequality.   

Normally I’d say “ let them marinate in their own filth if they are paying “ but in this case being it’s literally your next door neighbor and there’s a concern for health and sanitation of your unit , you might want to get rid of them now that the lease is up and see if the next guy coming In is cleaner .

Our economic system is complex, my suggestion is to learn as much about it from primary sources and listen to people on the internet as little as possible.