I have just done exactly that.
I am a landlord and know how long end of tenancy cleans take and how much having it done professionally costs. I often let to young sharers who have recently left University so know how naive and unworldly some can be.
DD and flatmates did thorough cleans of the kitchen and bathroom a couple of weeks before, but it was difficult as one had late exams, and DD had teaching right up until the last day of term.
You can only really clean when a flat is empty, so DD issued an ultimatum: either move out a couple of days early or help with the clean. One mum, worried that DD might be on her own came down, helped out and stayed overnight and then drove her DDs stuff home. another moved out early but had done more than her share earlier, whilst the fourth was never going to do much. I spent a day helping, both with the clean, and with DD moving her stuff from one top floor flat to another. When we got to the second flat it was chaos. The outgoing residents had not realised how much there was to do, so there was stuff piled up, with flatmates packing, and a mum frantically mopping the kitchen floor. The landlord has acknowledged it is filthy so it will be difficult for him to make deductions when DD leaves.
DD got her deposit back in full. Virtually none of her friends did, so financially it was worth it. I enjoyed spending a couple of days with her, helping her, and see it as a good opportunity to build the relationship with a young adult, and we had a lovely congratulatory meal when the work was done. DD gained from understanding and meeting contractual obligations, from scoping and delivering a project and gaining the support of others. All good life skills. Certainly a better result that a 21 year old not understanding what was required and suffering heavy deductions. How does that 21 year old learn if they are not taught, either by peers or by parents?