Does it matter if my wife/husband cheated on me while we were married?
When it comes to a divorce proceeding, the short answer is almost never. Bad behavior is common in divorces. Judges typically divide property and order custody of the children without taking infidelity into account.
There are exceptions, of course: If you have children and you separate from your wife and she starts living with a scumbag with a long criminal history (especially felonies, prison stints or sex crimes), you would have grounds to ask the court for supervised visitation and for Mr. Scumbag to stay away from the kids.
My general advice is if you are going through a divorce, don't start living with a paramour - especially if you have kids. You're going to make your spouse mad, which may make the case harder to settle and more expensive for you. If you don't have children, the impact to your case should be minimal.
But my friend told me I could get maintenance (previously called alimony) if my husband was cheating on me? No. That isn't the legal standard. Infidelity alone does not warrant an award of maintenance. Plus, don't rely on your friends for legal advice. When you need dental work, you call a dentist. Same with a legal issue.
Here is the typical maintenance scenario: A long marriage (preferably 20 years or more) with one spouse who stayed at home with the kids and did not pursue any education beyond high school who was supported by a spouse with a professional degree, a profitable business or other lucrative job. In that case, the spouse without any work history would not be able to support herself (sorry, but usually the wife) by getting a job paying minimum wage and still enjoy a living similar to what she had while she was married.
If all of those factors are present AND the husband was cheating during the marriage, the judge may take it into account when deciding whether to award maintenance.