You might just offer they buy, if they can get financing and you offer to pay some of their closing costs, as this often happens with a Realtor too.

Option one would be to assign the unwanted contract prior to closing and collect difference between the contract price I have and agreed to sales price with the assigned buyer and retain the desired property.

We then aim to close on the replacement properties as soon as possible after the relinquished property closes.

I had it for 9 years and now I'm closing in on 200 rentals.  

I had to come to terms with the fact that for many markets, small multifamily has become so overpriced that the numbers don't usually come close to making sense.

One of my buddies just wrote on a property close by to this that had 42 offers on it. 

These are just round number but close. 

I’m about to close on a duplex (hopefully) in December.

Talking to a few agents.Can someone guide me on the seller's closing cost details? 

I live in a ski town and write off the 2% (less where I live but close to correct in the Villages) as the cost of living somewhere fun and beautiful.