I would imagine you're going to have a difficult time finding one that's free. If you are going to be running a restaurant, you really should invest in a reliable POS program that will help you run your business successfully.
I don't know the price as I wasn't there when the system was put in place, but the restaurant I work in uses Restaurant Manager Backoffice, and it is very easy to use. You can find more info on their website:
http://www.rmpos.com/back_office.html
Good luck with everything, and of course keep us updated on your venture!