Some newer investors don't see that build date and potentially make a bad investment not realizing the amount of Cap Ex new systems cost.

Largest Wholesale transaction to date

If you have notice from an exiting renter, you can usually dove-tail their exit and the new tenant's start date within a few days.  

Lenders don't fund before the closing date and certainly not before approving a settlement statement.

I know your post is dated, but I have started looking at other comparable comps in the areas, using Zillow, Redfin, and the "Rent Estimator" on Bigger Pockets, etc.

For example, gives me $20,000 for down payment at 5% interest to be paid back by xxxx date. 

No one really cares about the closing time besides you the seller, and holding and closing costs can add up quickly decreasing your estimated net profit if the closing date keeps getting pushed. 

If you are not aware of what the rules are in your area, make sure it is specified in the offer in writing.I am not sure what the rules are in your state, so I might do something like this exampleBuyer shall inspect the property on (Date or between this Date and that Date. )  and shall have 3 days to accept the property, request repairs or cancel.In CA if any new  information is discovered and the buyer wishes to back out they have 3 days after the discovery to back out and get a full refund.

Being east of dahlia is also less desireable.  12 days on market hardly seems like cause to give up the sale... would have been nearly impossible to sell by Oct 1 with the list date...

Lots of steps, dates and procedures to follow.First, I would get up to date on what this tenant did right and wrong.