The one tenant worked at a furniture store and created "rooms" in the basement using cardboard and carpet remnants.

I have to agree with @Steve Vaughan, I'd say the same but I'm not licensed either.There was a time not far in the past when I would wish I could just bring cash in a cardboard box with me to a negotiation, just count it up and pile it on the hood of the seller's car until we agreed on a price.

Learn the eviction procedure for your area, perhaps contact a lawyer in the field to help you with this one, and get the fraudster you're currently housing out on the sidewalk to sleep in a cardboard box where they belong.You're going to lose plenty of money here, but this will never happen to you again, and you can minimize your losses if you move as quickly as possible.

For all you know I could live in a cardboard box.

As much as you want them to take down the cardboard or enter the unit, hold back and just let the process go through.

We would give them to Mexican brokers who would take them to Mexico and replace them with card board shanties.

Another option for the ceiling is drywall over it or skim coat it.... if it's those square cardboard looking tiles then just sheet rock over it with 1/4 inch drywall.

It should work with the caveat that you stay away from the standard tiles that are made of pressed cardboard or whatever it is.

At the time it looked like an ideal business with very quiet tenants (cardboard boxes and golf clubs don't complain very much).

One recorded eviction on their state record and they'll never rent a dwelling again significantly better than a cardboard box.That being said, there's ALWAYS A risk in these cases.