At closing I received the lien waiver and receipt for the work completed.The problem was that the contractor had not removed all of his equipment from the property.The next day they removed one of their two trailers.

Not only are you going to loose money through vacancy, but imagine what the cost is going to be to prepare the property for another tenant.

Takes a while and you must have the volume and balance sheet to warrant the fuzzy little feelings the banks need when removing you from the personal liability.

But that makes the sizes of them difficult to make homes, so you remove walls, which makes the engineers cringe......You've probably heard all this before from more reputable and authoritative sources than myself, so I won't be long-winded, and I definitely won't be a naysayer. 

Don't mistake this for loosing sight of the number, just don't make it all about numbers.  

One of the pieces of work included was a complete rewiring of the house to remove the active knob & tube system.

She just received notification from the bank that she has 15 days to remove her belongings from the property.

The longer this occupant remains, the more difficult to remove him.

First, i would not furnish the places, it will probably get trashed, let them get there own furnishings and make sure that the lease says they must remove them from the property when they leave. i would have them pay for utilities, to an extent - have them pay for electric, supply the heat but give them an allowance for certain amount of months ( especially if you have older furnaces and they run on oil heat ) if they go over then you charge them for it. i converted mine to gas with new furnaces, i include heat in mine, but i control the thermostat ( online, thermostat is locked at the house ). i also provide water / sewer and free internet.

If you can have an addendum of removing the clause and seller is ok with it then you should be good.There will be local REI in NJ depending on your location where you can meet these guys.