initiation fee; registration fee; sign-up fee
A one-time fee paid when joining an organization, club, gym, or similar group.
This gym has no initiation fee.
The initiation fee and annual fee are charged separately.
月会費 is a monthly membership fee, distinct from the initial 入会費.
Compound of 入会 (にゅうかい, 'joining') + 費 (ひ, 'fee').