Summarize:

Depending on the amount of personal property you have or whether you have children, you may feel the need for a lawyer. Lawyers charge by the hour and the rate is often above $300 per hour. Even if you don't need a lawyer, divorce will cost you in many ways: Your assets will likely be divided. This includes your home, vehicles, retirement, and savings. If either of you signed a prenuptial agreement, you may walk away from the divorce with little to nothing. On the other hand, many prenuptial agreements have a "cheating clause" built into them which could leave you paying out a large settlement. Depending on your financial situation, you may be required to pay your wife alimony after a divorce. Even if you don't get a divorce, simply separating is expensive. You will be dividing your household income into two sets of bills such as rent, food, and utilities. This will put further strain on your marriage and lifestyle, and likely lead to a divorce down the road. If divorce is the outcome of your affair, your children's lives will change dramatically. They will no longer live with both of their parents all of the time. They will have two homes and two families. They may even have to change schools, move to a different home, or move to a new state. Though cheating may not always have a direct effect on custody matters, it will likely push the court to judge you in a harsher light. In the event of a divorce, your entire family, including people like your mother or brother, will be losing a family member. Some members of your family may have gotten very close to your wife. They may also feel hurt and betrayed by your indiscretions.
Think about the cost of divorce. Double your living expenses if you separate for a while. Consider the emotional costs to any children involved. Think about extended family.