Half of Duplex - Need Roof

[Gerald Pitts]

In addition to a 2nd rental I'm selling in Nashville soon, I'm selling my half of a duplex aka zero lot line property in order to buy my 3rd vacation rental in the smoky mountains. Seller is requesting a new roof after inspection revealing roof to be super old / shot. All of the roofers contacted are saying they can't really do half the roof of the structure. Total roof estimate is $6300. I spoke with the owner next door who is also intending to sell as it turns out. But she is not interested in replacing the roof and is selling as is. I relayed what my realtor was saying that the likelihood of either side selling without a new roof is highly unlikely. She wasn't interested. I told her to let me know if she has issues selling and changes her mind. 

HVAC is also shot, but they are only asking for a home warranty and not new hvac.  We asked buyer if we could just provide a roof allowance, but they are insisting on the replacement of roof since they aren't asking for hvac.

 In total, they are requesting roof, warranty and seller paid closing costs.
Roof for both sides = $6300
warranty = $550
Seller paid Closing costs = $3300

Net gain is the difference of roughly $25k replacing whole roof vs or $28k with skipping roof altogether and re-list risking a dip in price of 5k according to realtor. Also, the next guy could ask for a roof and an hvac.  If I had the capital, I'd try to buy the other side of the duplex, but I don't.

The painfully evident choice seems to be to eat $3k, replace the whole roof, and move onto buying the next Gatlinburg vacation rental cabin which will make back the $3k in no time.
I just wanted to put this out there to see if anyone sees an additional option I'm not thinking of?