Help! To seller finance, conventional, or run away??

[Sage Baca]

I’m in the negotiation stages (using a real estate agent) of a property I believe will make a killing via Air BnB once its fixed up. Here are the details:

Prop originally listed at $400k, then $375k, then removed from listing after 9 mo. I met with the sellers personally and got the impression their real estate agent advised them to sell to a cash buyer (assuming a bank wouldn’t finance d/t to the property condition). My “unprofessional” opinion was that the property didn't need so much work that a bank wouldn’t touch it.  But I could be wrong.

Offered $340k (original list price was $400k). Seller’s accepted and agreed to seller financing, then changed their mind because I could only put $10k up front, with an additional $50k pending the sale of my current home.

We countered with the conventional route (which saves me a lot of capital) and are back and forth about inspections. I agreed to pay both well water/sewer, but asked the sellers to pay for any repairs if any were needed.  They offered up a max $2k allowance for repairs.  

We did not accept this offer, and now they are talking about seller financing again. 

My question is, how can I make this deal work? Who can I bring along to help me figure out if there will be any issues in these areas? Would an appraiser or inspector be able to tell if there were any real issues with water/sewer/structure? 

FYI, if this property (with 2 buildings) is fixed up, I believe the ARV will be around $525k-600k. Cosmetically, I plan to put in about 75k. It should rent as a vacation rental for $9k-$10k/mo (cash flow $3.5-$4k/mo).