That's a big benefit to do exhaust hoods...just save a vacuum full of nice greasy water, and if the customer doesn't want to pay, they can have their grease back...all over their kitchen:)
Seriously though, I've only had one problem with this, and it was a corporate account. Payment got tied up at that end because of paperwork issues, but did get resolved without anything more than a few dozen phone calls. Most of my customers are COD.