A slight correction to what Mike just wrote regarding Catholic priests (and this actually applies to the Orthodox Priests as well). Priests cannot marry. Period. (Neither in the East or the West.)
Eastern Catholics and Orthodox, routinely ordain married men. There is a difference. Once ordained, a man cannot marry — that goes for Deacons as well who, up until recently, were also referred to a Reverend.
In the Western Catholic Church or Roman Rite, we almost exclusively ordain unmarried men but we do make exceptions.
That is the situation among Catholic and Orthodox Christians.
Protestant Ministers, who are also Christian, are allowed to marry both before and after ordination.
With respect to your last question, there are no limitations on marriage for Protestant Christian Ministers. The same holds true for married Deacons in the Catholic and Orthodox Church, however, with respect to married men who become Priests (again either in the Eastern Catholic, Eastern Orthodox, and those exceptions in the Western Catholic Church), there are some restrictions with respect to the exercise of marital relations.
I'm not positive on the time span but I know that they have to abstain from marital love before celebrating the Divine Liturgy. I believe it's something like 24 hours. Certainly the priest is not supposed to have sex the night before he celebrates the Divine Liturgy where he will be consecrating the Eucharist.