Still not 100% sure what I will do at the end of this (we are a long, long way from the 3.5% rates and hot, hot sellers market of December 2021/Jan 2022 when I started looking into this). 

Seller financing means I enjoy 30% ROI YoY.

He's talking about motivated sellers.

Locate a Motivated Seller that will consider Seller Financing.

He ended up taking my underwriting/origination escrowed money and strung me along for six months, frustrating me, the realtor, the seller, and making my negotiation potential crumble.

No, banks do not allow a seller held second now a days due to risk and new guide line changes. 

Most sellers are looking for 70-90% of the legal payoff nowadays no matter where the property is located, which in many cases is well above the unpaid balance. 

The seller can supply everything they used to market, pictures, ad copy, etc., but they cannot sell their AirBnB account to another person.

Unless the seller has to be immediately out of the mortgage I see sub-to as an excellent cost reduction strategy. just reading between the lines.. but if the bank says they will take 91k for it sounds like the mortgage is in default so a sub to might not be possible.

Don't buy a 2br/1ba without a basement and no garage on a corner lot next to the scrap yard, just because it's cheap and the seller is motivated.