Multimillionaires die every day after they forget how to breathe, sagging off the pot.

Why are you going elsewhere looking for your pot of gold?

You may be able to give them notice and they will move out voluntarily.

Unless local law says you have to approve the first qualified applicant it would be foolish to voluntarily accept the lowest common denominator because they applied first

Who knows, they may voluntarily move out, in which case it would be sooner that. 

I worry that if I hold on to them for 10-20 years, they may literally fall apart and then I am just left with a big mess and a pot of land.Has anyone had experience with buy and hold investing of manufactured homes? 

If the deed in lieu conveyed the property to the previous lender, that sounds like a pocket deed that was not executed voluntarily and for value.

Best is to tell them you will file for eviction but you are willing to offer a few hundred bucks for them to leave voluntarily (cash for keys).

Secondly, I am having trouble wrapping my head around the kind of returns that will be gained from so many hands in the pot. 

Aside from the pots of gold, what do you generally look for when seeking a property to approach?