I'm open 7:30-5:30 and I charge $40 a day. If you're here the entire time, it's still only $40 a day. I don't charge more if they're here more. If they wanted to be here before ore after opening or close, I would charge $3 per half hour per day. (This is just what I do). As for a holding fee, I would take a security deposit of two weeks, and then charge $200 a month. That's just me though.