Laptop as a mobile hotspot?

If I use the laptop as a mobile hotspot and use it to give a friend the Internet, does it cost money? I don't have a contract. This is our own Wi-Fi.

If I understand correctly you are running a so-called "repeater", so you route your Wi-Fi to your friend via your cell phone and that is free of charge or the same price as going into Wi-Fi

If you share your own Wi-Fi via hotspot, it costs nothing extra. But your friend can also log into your Wi-Fi directly, provided you give them the access data, or you set up guest access for your friend if the router has an option for guest access.