Wifi for coffee shop

[Vanisher]

Hello, colleagues, I have a question, I've been searching, and I don't know where to continue.

It's about cafes with internet access for customers.

How do you set up a network like that?

If you give the password to the customer for having a coffee, you have to change it every day, so that they can't access it from outside, or worse, if it's a neighbor and they can pick up the signal.

You can't leave it open either.

Of course, in the cafe there is some computer of their own, so you can't compromise its security.

And all that without spending a lot of money, if possible, with the router that the ISP gives you. Has anyone ever installed a wifi like that?
Captive portals? How do they integrate?

[packosoft]

obviously and for security the computer or computers should not be on the same network as the clients.
I have a router at home that allows you to create a normal wifi and one for guests.
Regarding passwords, if you use the same one for all clients, obviously you would have to change it every so often. If it's something more elaborate you would have to use kerberos authentication, with a validation server and so on, but I think that's too complicated for a cafe, right?

[Vanisher]

For now, no one has asked me for anything. They have simply asked me. The thing is that I didn't know how to give a concrete answer, because I have never done this before (and they do get to do some strange things with networks, but not this).

So it's something that's more or less widespread, the thing with cafes with wifi, but it's something that I don't know how to solve.

So in principle, to keep it simple, it would be enough to have one normal wifi and another for guests.

Can you password protect the guest one? Can you make that password expire? Can you give the network a different name?

Because, to start, that would be a good approximation. What router do you use?

Then it would come to "if you spend €5 you have 50 minutes" (for example) or a download of X megabytes...