I know every partnership is unique and it really just depends on the two parties involved, but having the general opinions of other investors will help us to understand more about what we should or should not expect. 

The lease document is there to protect both parties.

A qualified 3rd party intermediary makes everything easier (also required) and if you don't have another deal or property lined up or in the works it makes the process 10X more stressful.

I've read conflicting information about what triggers you to have to pay self-employment tax on your short-term rentals.There seems to be a consensus that the following does:Airport TransportationProviding cooked mealsOffering ToursCleaning during the guests' stayDecorating the property for a party as a serviceI'm not sure if these would cause me to have to pay self-employment taxes, as I've seen these items on a couple of lists but not most:Providing a coffee stationProviding a welcome basket with food itemsProviding bikes and kayaks for the guests to useDoes anyone know where the line is of what you can and cannot do and provide?

At that point all parties new that I was serious about the deal.

When going after damages you need to prove that you tried to mitigate damages (i.e. relisting it with the intent to rent to another party).  

What did both parties do exactly?

The third and fourth fixed and same as the second. 

The divorce details could make this a trickier process but the party who wants to sell can file for a partition to have the court force a sale.Another option would be for the person who wants to keep the property to get a refinance, take the other borrower off the loan and execute a quit claim deed.

It seems like the tricky part is to determine what amount would you start your offer that would seem to be generous enough for them to consider / take / start of as a negotiation point.