When a man goes through a divorce, he doesn't necessarily lose just his marriage; sometimes, he loses his home, too. Laws vary by state, and decisions can be at least partially based on individual circumstances. However, losing the right to physically live in the home does not necessarily mean you will lose all of your equity, even if your wife purchased the home before you were married.
Whether you live in a community property or equitable distribution state, marital property is usually defined as all property earned or acquired by either spouse during marriage. Marriage begins on your wedding day and ends on the date of separation, date of divorce or whatever landmark end date your state specifies in the law. Your entitlement to the house is based upon the extent to which you bought or paid on the house during marriage. If your wife bought the house in her name after you got married and before you separated, that house is at least partly yours, unless she paid for it with the proceeds of her own separate property.
If your wife bought the house before marriage, you may have a right to some of the equity in the property if she made mortgage payments or improvements with funds earned during marriage. Courts will consider the mortgage principal reduction made using marital funds and any increases in value traceable to improvements. If she owed $100,000 on a $110,000 house on date of marriage but owed only $90,000 on the same house on the critical date of valuation, $10,000 of the equity is her separate property and $10,000 is marital. Depending on your state, you're entitled to generally half of the marital portion.
If your wife owned the place before you got married, she'll probably get to keep it during your proceedings. Even if you bought it after marriage in both names, though, you could find yourself looking for a new place to live. If you're the one who left, the judge will probably award at least temporary possession to her. Furthermore, if you have kids, and she has primary placement, she ran you out on a domestic violence protective order or your cohabitation had to end because of some kind of misbehavior on your part, expect to lose possession of the house. If she can't afford the payment, the judge can sometimes make you pay for it.
No matter who gets temporary possession of the house, eventually the equity will have to be distributed. In your equitable distribution or community property case, you will have to decide who will buy whom out. If neither one of you can afford a buyout, you'll probably have to sell the house and divide the net proceeds. Buying out your ex's equity doesn't always require cash, though; depending upon the makeup of your marital estate, you may be able to compensate her for her share of the equity in a home you want to keep by giving her more marital property or less marital debt elsewhere.