Maybe it wound up "growing" something in the sump, any way.My question is:Do you think it would damage anything if I dumped a couple gallons of distilled white vinegar down there to see if it would loosen / dissolve the scum?

This is the only way to learn.. lick your wounds  and keep  going... 

I'd also show him the option of having you list it on the open market/MLS, what the pros/cons are, how long it wound take, and what price it may fetch.

I've licked my wounds and ready to get back in the game.  

He wound up buying a potential Cashflowing property in Staten Island in a very poor location.

Tried to switch to Dashlane when Logmein bought out LastPass but wound up going back.

It wound up being about 18 months, but we had our buyer lined up for most of that time, which made the bank more cooperative.

Otherwise, you risk running out of reserves part way through, as Jeff above alluded to, and more prepared investors will be only too happy to come in and pick up the pieces while you the newbie investor retreat to lick your wounds.

I am one of the program directors, and I could just walk away from the whole thing and lick my wounds, but aside from needing to move ahead for my own financial benefit, I feel responsible to the the people I recruited based on the original template I was given, and I don't want to see them robbed of their hopes and aspirations. 

And actually I wound up with a 12,300 check at the end of the day, plus a refund of about 600 from escrow account on loan.