Church wedding donations?

Hello!! My fiancé and I are looking to get married in a church but I am only the second of my cousins to get engaged so not sure where to start. I recall getting married in a church is "free" and you're meant to give a donation to the church, but does anyone know how much to donate nowadays? My parents' experience 30 years ago is helpful but not really current, we also haven't been to church in quite a long time so there's not really any parish members we would know to ask.