For the purposes of this question I'd like to give an example period/location of the Italian city states in the 15th century. Mainly because of the (arguably) high religious fervor of the time, and also prevalence of such organisations as the Medici banking family.
Check out my comment in this thread. I can answer followups as well: https://www.reddit.com/r/AskHistorians/comments/3025o5/when_did_it_become_acceptable_for_christians_to/