On the other hand, if the tenant does deliver the rent and we can get through the winter, then I would be in a better position from the financial and rental demand standpoints.  

Back before there was email and internet people serious about buying property would hand deliver offers and meet in person with checks in hand. 

Contract is not bidding until both parties sign AND IT IS DELIVERED!

If they deliver that would be a plus.Thanks.

It is honestly too hard to tell given I don't know what original site conditions look like, how much dirt has to be moved, are they having to import water to assist in compaction, how much excavated fill will have to be disposed of off site, concrete costs per cy including all fees to deliver, rebar costs, pumping or no pumping, -- looks like you are going to have 2 mobilizations,,,, one for the footing and the second to pour the slab..... there are a lot of variables here..... 

If buyer fails to fulfill his obligation under this real estate contract or buyer fails to close this transaction, the down payment is not refundable to the buyer unless failure to close is exclusively the fault of the seller of if seller cannot deliver marketable title to the property.  

In your offer, add the condition, "To be delivered vacant at COE" and it becomes the sellers problem.

Box stores will deliver and haul the old one away.

I never flip- flipping is a full time job that delivers close to zero tax write offs and zero passive income and it's risky if you don't know a market first hand and have a trustworthy construction/rehab team in place. 

Id either look for a used fridge from a used appliance store that delivers ($200)  or a cheap new Fridge($400).