if you are reserving the church for any length of time for an elaborate ceremony with bridesmaids, photos etc. you will pay the same as for a regular wedding, whatever the going rate is, and offer a donation to the priest or deacon who officiates. You can ask what a usual amount is in your area when you make the arrangements. The groom or best man usually hands an envelope with the donation to the presider.
If you have organist, soloist etc. they will tell you what they charge. It is nice to tip altar servers if there are any $5-10 each.
If you are having something much simpler such as exchange of vows after Mass for instance, there should be no charge for use of the church, but a donation for the priest or deacon is customary. again, ask when you make arrangments. $50-100 is usual around here. bear in mind it is not mandatory and is not a fee, just a donation. also, before someone asks, yes it is reported as income to IRS, unless the priest opts to give all such donations to the parish general fund.