The only business activity available is to do laundry, but sims won't wait for them or try to dry them. They will literally put clothing in the washing machine and leave the business a few moments la...
Ideas
Adding weight to the post, have just created a sim that has made a laundromat (small business residential). Some customer sims will put loads in the washing machine, occasionally they will subsequently start the wash, but then they do nothing. Many sims will go to put washing into the machine, but will bug out and it will dump a pile on the floor (it might be that one of the things for customers to do is read books, I notice they also dump a book on the floor beside the dumped laundry pile.
My workaround for gameplay is to set up some sales shelves, have my sim complete the wash/dry cycles (including washing the laundry on dumped on the ground), and then set it on the sales shelves - my head canon is that sims who are purchasing it are paying for her to wash their laundry and returning next day to collect it, ie paying on collection).
But of course, that is not true to how a laundromat works.