You think a seller would want to find out the day before closing, after they've moved out, that you can't get financing and you get your EM back, no harm no foul?  

Apparently this is not uncommon, maybe I should say "obviously"    http://www.biggerpockets.com/renewsblog/2012/11/05/getting-rid-tough-odors/

The deposit covered the odor removal and for new carpets and pad.

From Gordon Gekko to Bernie Sanders to The Wolf of Wall Street, Main Street has continued to cry foul and yet bonuses are as big as ever, even after the taxpayers bailed out the banks.

I hear ya on Inner city Charleston though the main issue there is so many buggered up title issues you can spend all the money on marketing get what you think is a screaming deal and the title is so fouled up it will cost 5 to 10k to clear up and take years.

Also, look for the low odor VOC formulas, too.

It's not so much poo, as urine, urine....wow....just foul.

I you get the HELOC and change your mind, no harm no foul, as long as you haven't pulled any money out of it, it doesn't cost you too much or create a recurring payment or mortgage due.

If the current tenant is creating a problem from a curb appeal stand points, has odors coming from the home,  or is otherwise degrading the value or safety of the units, I would definitely move them out if you are able.   

The best is BIN because it is shellac based, but any oil based primer especially those that say smoke or odors.