
When operating any wifi system, you have some choices as to how restrictive you want to be about who can use the system.
Typically, in a restaurant or cafe or waiting room situation, wifi access is open to anyone within range. You may or may not require that they also know a password. And you can change the password as often as you like.
If you are running a hotel or motel, you may want to restrict access only to paying guests. (You may even want to charge for the service.)
In this case, you should consider a username/password authentication system.
RedHotSpot can provide user/password authentication service. The cost of this service is $9.95 a month. You will receive a list of usernames and passwords, which you can make available to users as you decide. Usernames are good for a fixed amount of time, after which they are invalid. Active time can be an hour, a day, a week, or whatever you specify.