Christians should not themselves be prostitutes, or in general have sex with multiple partners outside of marriage. However, you're asking about having a spouse who's a prostitute. I don't see this as a sin, if you're faithful in the marriage. Note that Jesus is recorded in the gospels as having been friends with "sinners" (which probably included prostitutes).
As a practical matter, be careful of STDs. If you have a partner who is a sex worker, he should be tested frequently for STDs.
As for marrying an atheist: In these days, when it is so hard to find a marriage partner who is a practicing Christian, many Christians do end up marrying non-religious people. I'd recommend having these conversations before marrying: Is the spouse going to support you in your faith? That is, will the spouse respect that being a Christian is a good thing to be and do? If you're going to get laughed at every time you go to church, that's going to be hard. If your spouse respects that your faith is a good thing in your life, even if the spouse doesn't share your beliefs, then you can probably work with that. Additionally: If you have children, is your spouse okay with the children going to Sunday School, being baptized, and so on? Work out all the interfaith details before you get into the marriage.
Blessings to you, ForsakenGirl. Being a Christian in this modern, secular age isn't easy.