I set up machines for wireless all the time and the cheapest and most effective way I accomplish this is by getting old WRT54G wireless routers and flashing them with the DD-WRT firmware and turning it into a bridge that connects with the customers existing wireless network. You can use the QoS settings to manage bandwidth with respect to the printing and scan functions to keep complaints about network speed to a minimum. DD-WRT has a lot of features and is a pretty useful appliance in general. It's a good solution as long as there isn't an excessively high volume of printing and scanning going on. Some manufacturers sell wireless and bluetooth kits but the advantage of using your own bridge is that you can run an ethernet cable to it wherever it's at. So if you are in a spot with poor signal you can move the bridge around and monitor the web interface for the best signal, then run your cable to it.