I've wondered about this myself - make sure you consider the cost of transactions when you decide. Some will have a processing fee for every swipe and don't batch them. If I put a
Hamilton unit on one of our vacs and charged $1 per swipe, we'd lose a third of that right off the bat.
Are there combo vacs with built-in CC acceptance? Do they allow for variant timing for the different functions like they do with cash? My problem with add-on CC and count-up is that the customer will end up paying the same rate for all the functions, i. e. for $1 they'd still get 4 minutes of fragrance. Now I doubt any idiot will spray fragrance for that long, but they'd be able to vac for 3 minutes and use fragrance, and we'd lose out on an an additional $1 purchase.