Performing religious service requires access to, and often attendance at, a temple whose beliefs and ethos align with the character’s. If such a place is available, the activity takes one workweek of time but involves no gold piece expenditure.
Characters with a religious bent might want to spend downtime in service to a temple, either by attending rites or by proselytizing in the community. Someone who undertakes this activity has a chance of winning the favor of the temple’s leaders.