There is co-op water close so that is not a problem but I'm not sure how the aerobic systems would work out.  

Since the seller doesn't have much equity it's more than likely not going to work out.

Now that's sort of regardless of equity, but if the borrower has equity in their property and realize it, they may be more inclined to do a workout so as not to lose it.

I know you to be a good judge of peoples character-- I am sure it will work out for the best, we are all just worrying for you so that you do not have to.

Hey Ben, I'm looking to purchase a condo/property in Riverside as the numbers (purchase price) work out better for me, so I agree with you on the 'making sense move.'

Maybe we can work out a deal. 

In this situation, it is my recommendation that you work out your contract to be the one who benefits from the negotiation.  

Worst case scenario is a situation like yours which we all see how horrible it turned out, but best case scenario is none of the numbers work out and you don't lose much money but you really don't gain anything,  and therefore the whole experience is really like sitting in cash and therefore not even an investment.  

I guess now, I will look into an equity loan/ line of credit or possibly selling the duplex to get myself more cash flow if the numbers work out.  

However I would have a contract that makes earnest money non-refundable so if they do this switch and it doesn't work out then you have something for your time.This buyer might never have had the 20% down.