The seller has no reason to give it away for 20k if he can foreclose and collect 60k, so it warrants a higher sales price.The BK example above doesn't seem to fit this description and is most likely a pass. 

If is warrants further attention, then go visit.

How to i proceed to legally remove them if warranted?

That doesn't mean you come up on a house that doesn't warrant it, just that you don't pick numbers out of thin air.

If there is lots of banging that is ongoing, I would try to limit that to during the day and also work to get it done fairly quickly to minimize inconveniences to all, but renovations and remodeling continues and tenants should expect it periodically.If renovating theirs, I would do it at lease end to warrant rent increases and I certainly would not evict the whole building to renovate, that's kinda silly and unnecessary. 

I could not see anything on the appraisal that warranted the low appraisal. 

The area you are in might warrant it, but if you can; I would try and rent the unit to someone that can pay rent on their own and you might (and probably) will avoid situations like this in the future.

I used electric baseboard heaters in one of my rehabs that did not warrant installing CHA

You need lender who can offer non-warrantable condo loan.

If my mood warranted it I might even threaten something back, even if it was bogus, just to play with her mind.