People are floating their stuff on air mattresses and in fridges.

Their parents will pay for any furnishings, or they'll just put down an air mattress and only sleep there.  

You don't necessarily need to go that far, even a 4-6" "topper" of blown cellulose will greatly reduce air leakage into the attic & that's what you and your tenant both want.  

LolI didn’t know you can rent mattresses!

I once stayed in a beautiful cabin with an amazing hand made log king size bed, the mattress height side rails were logs with the bark still attached.

Why is he charging for mattresses? 

: There were screens missing from some of the windows upon move-in which we authorized maintenance to replace (they were backed up several weeks due to COVID shut down), A/C wasn't getting the apartment cold enough even though it had been serviced within the past year (set at 68F during the hottest summer we've had in years in Michigan) and we didn't offer to pay her electric bill, found a bat in the basement x 2 which we had professional pest control there at their first available appointment and they didn't find any evidence of a colony but we had maintenance seal off any areas in the basement that could allow bats in, and now a water leak from upstairs apartment overflowing their toilet onto this tenant's mattress.  

Hi All,After inspecting the attic and talking to the tenants, who were generally very calm about it, I discovered a thin layer of soot from the original sheathing material on most everything in the attic.The main thing that is claimed as ruined is a baby mattress for the crib, which I offered to replace.

We had to remove baseboards, pull up carpet, replace boxsprings, disassemble furniture and put it out in the shed (at -25C for a week).By the time we were done three treatments of the entire lower unit in the building and inspections of the upper unit to ensure they had not spread that far and had replaced mattresses and boxsprings -  we had spoiled the better part of $5K.Since it was a rooming house, we had to act quickly and assume the costs - the tenant skipped anyway (and has no money).  

And for all you know, she has a bundle of cash in the bank or under her mattress that she's been saving for the inevitable day.She is not your mother.