I´m not sure what
the extent of your knowledge in this area is already, and I did not mean to give you the wrong idea in my last post. Ideally, a hardware based routing solution would probably be the most foolproof way to run your successful internet cafe business. However, the most desireable hardware routers come with a pretty hefty pricetag these days, and as it does not sound as if you are actually already doing this, I would want to make sure that you are able to do a successful business here before advising you to invest in something like this. For a limited time, at least, Linux can help get your place going.
In the long run, though, if you end up doing a good business, and can afford it, I would strongly advise upgrading to a reputable Hardware based routing solution.