You can sell vouchers for cash in your hotspots. Voucher codes look like: ‘1h-42342342′. This code needs to be entered in the voucher activation box on the splash page, or as a username directly into the login box.
Optionally you can require a user registration for vouchers. In this case users can choose a login name and password which they can use to log in to the hotspot instead of the voucher code.
They can also activate a new voucher with the same username and password in the future which allows them to use a permanent login name and password instead of a voucher code which is hard to remember (however you can also display a “Remember Me” checkbox at the login).