hi Friend ..
Listen that sounds like a nice idea.. whenever you deal with money is a good idea!!! Anyways .. here every bodyknows that in order to deal with a USB connection is better to go with a solution that is complete ,hardware + drivers .. There are several of those .. but the most obvious is FTDI from
www.ftdichip.com .. they will provide the drivers for free.. So you wil be able to deal with just your project
idea .. otherwise .. dealing with drivers . can be a nighmare if is your first time . FTDI will provide you with samples .. and the chips are cheap !
good luck !