Does it cost money to use the Helium Network?

Hello there, I'm curious about the Helium Network and I was wondering if there's any cost associated with using it? I've heard a lot about how it's a decentralized wireless network powered by people, but I'm not sure if that means there's a fee for connecting to it or not. Could you please clarify this for me? Also, if there are any costs involved, what kind of fees can I expect and how are they calculated? Thanks in advance for your help!