This process can be very costly, requires zoning permission, in addition to all the items you listed.

But I'd suggest to not get caught up trying to hit a home run on your first deal.

What additional information would be helpful to get a better understanding of this deal (e.g., demographics, tenant mix, operating expenses breakdown)?

That would be my suggestion.

When we had more properties we would increase it, but it was not linear, but for me comfortable would be $20k for the first property and $5k increase for each additional door on top of that. 

Great suggestions.

You missed the salient question -- Lender has borrower liable for loan --- a wrap occurs -- there is now a new person (in addition to the first) that is liable for the loan -- 2 people are liable -- how does this decrease the security of the lender -- they still have their "approved" borrower -- and now they have another -- approved or not -- they have 2 -- 2 is better than 1 -- yes?

Unfortunately, the majority of investors that experience terrible service from turnkey companies, figure out that it's not worth spending tens of thousands of dollars suing their turnkey provider and just move on - which allows the turnkey provider to not change their ways and stay in business:(You should also check out this BP thread about the topic:https://www.biggerpockets.com/forums/88/topics/976647-turnkey-company-suggestion?

If you are willing to expand your search a little, I'd suggest more traditional vacation markets in parts of Wisconsin and MIchigan.

If you decide to sell and have not done it before, I might suggest using an agent.