When the previous "tenant" move out before 2009, there were multiple mattresses, even dog cages on each bedrooms/floors.  

You mentioned mattress was directly on floor, its apparently really common for mold to occur under a mattress thats placed directly on the floor.

Everyone 's likeness on mattress is so different so how do I make everyone happy?

Most of us can keep our money in a mattress so the point of banking in 2012 is services -- offered at local branches by real people!

There's a mattress, frame and a refrigerator that's still in there.

Threw the old couches, mattresses, dressers, general trash, diapers, etc into the swimming pool, ruining the plaster, smashed all the water turn off valves under the sinks and washing machine with a hammer, tub full of **** and urine, clogged with a towel, toilet pulled from the floor, stove and oven smashed with a hammer, etc. 

I'm surprised these same people don't have all their cash stashed inside a mattress, because [insert latest conspiracy theory here having to do with the gold standard].

You sound like you're probably headed for deep and shark infested waters on an air mattress, (LOL).Land contracts are pretty well dead in the water, two issues, one is with the new laws pertaining to seller financed transactions, if you pass a lending contract on to a buyer you're facilitating a loan assumption and doing so as a business may have consequences.

His thought was to replace the mattress and all would be well.

A 6-10" "topper" of blown in cellulose would likely cost less than $1k professionally installed.