It is very early for you after discovery (and I'll remind the other posters that the OP's started this thread... yesterday). Coming from someone who's been around the block a bit I thought I'd remind you of a few things.
This is not a court of law. No one really "wins" and no one really "loses." Your wife won't be "homeless" because, since you're the primary breadwinner, you will need to provide her with basic support, at the very least. Furthermore, you already know what's going on - I don't think that you, or anyone reading this, would think to themselves, "Yeah, he's just a friend." Everyone, including your wife, understands what the situation is - meaning, no one is in the dark.
So let's take this from THAT perspective. We're all in agreement that your wife is doing something totally unacceptable.
What is the goal here? It's to move YOU out of infidelity. It's not to save your marriage or even to make you feel better. Often, feeling better takes years - no matter what action your wife (or you) ultimately takes. You need to get yourself out of this shitty situation.
Think about this for a second. Your wife is doing something (no matter WHAT it is) that is hurting you terribly. I would hope that people don't get married for that purpose. A wife who is PURPOSEFULLY hurting her husband, and who KNOWS she's hurting her husband... AND WON'T STOP... is a special type of a-hole. Look, I get that people have affairs and now, after years of dealing with this, I get that people in an affair don't think about their spouse. But your wife DOES. She KNOWS that you know and she's still unwilling to end it. She is now hurting you ON PURPOSE.
So what do you do? If she was taking a hammer and hitting you on the head you'd ask her to stop. If she kept doing it you'd finally get angry and put an end to it. You'd take control of the situation and do what you needed to do in order to stop her from hitting you.
So do it! Tell her, directly to her face without any anger - but in a way that she knows that you're not fucking around - that her interaction with this guy ends immediately. If he's a coworker then she quits immediately. No further contact, etc. You know the deal. In short, you lay down YOUR requirements in a way that is perfectly clear. Then, simply let her know that want to try to work things out but you cannot and will not work anything out while there's a third person in the marriage. Lastly, you let her know that, since there's another person in the marriage, you will be taking steps to end the marriage unless she decides to change her tune.
Then... and this is super important... stop being the cash cow. Do you pay for her phone? Cancel it. Does she have internet access at home? Cancel your coverage. Is her car in your name? Return it or sell it. Tell her parents. Tell her siblings. Start making it difficult for her. Let her see what life is going to be like as a divorced woman.
Last thing - if I could live the last 6-7 years over again there is ONE thing I would do... and that is to have been stronger and firmer in the days following discovery. I should have laid down the hammer and found my balls sooner. It is the one regret I have in life... and I am fully and totally reconciled with my wife.
Please, think about that. If your marriage survives, great. But no matter WHAT happens, you will always have to live with yourself knowing how you acted in these early days.
Good luck!
[This message edited by LifeisCrazy at 9:31 AM, July 16th (Monday)]