I understand that it can be a challenge to appear confident when you're not. 

All of my 4 properties cashflow and appear on my tax return.  

However, the language in the the first item and the email response does make it appear the seller would be handling at least that first item. 

It appears that the property has other issues like aluminum wiring that seems to be uninsurable. 

We have to wait for that newly published book's income to appear on tax returns, but by that time the initial rush of book sales will be over, and YTD will be less than historic (and, thus YTD will be used), unless you're constantly putting new books out, hurting your calculated income.

Asking for owner financing up front makes you appear as if you don't have any money and are not serious/able to purchase their park.

Make it clear if they attempt to break the lease before you find a new tenant you will take them to court for full compensation.

It could be everything from a court order to sell, or a Quiet Title Action (you need an attorney for this one) to needing an affidavit or two, to "you are good to go "as is" (I wouldn't expect the last option to be the case.

It also appears that the back corner of the lot is in a 500 year floodplain.  

Ask yourself what would a judge/jury think if they took you to court?