How much your divorce will cost depends on you.
You have to stop thinking, “but it’s mine because I paid for it”, “I want revenge”, “I do not owe him or her anything because s/he left”, “It is the principle of the thing”, and try to take your emotions out of this. Love is grand. Divorce can be two grand if it is uncontested or 20 grand (or more) if you want to fight. According to Lawyers.com, in 2015, it cost $13,000 per person to get divorced in this state, on average.
Once you have reached this point, you need to come up with a list of your stuff. Make sure you list the house, checking accounts, savings, retirement funds (you know, the 401(k) through your employer), cars, boats, animals, investments and furniture. Agree on how this is getting divided. Try to be fair and reasonable.
Now make a list of your debts. If you are not sure what you owe, get a copy of your credit report. Divide this up.
If you cannot do all of this in one attempt, take several tries at it.
Many parents get stuck on the title of being the custodial parent. The legislature has changed the law, removing the title of 'custodial parent' and, instead, calling it an allocation of parental responsibilities. No matter what you call it, what it means is who spends time with your children, how they see both of their parents, and how parents make decisions for them. The reason that some parents get stuck on the title is because they think that being the custodial parent means that they get child support. Other parents think that sharing the kids 50/50 means they will not have to pay support. Neither of these is true. There are cases in which the parent with more time pays support to the other parent. There are cases in which the parents share time, and one parent still has to pay support. Finally, some parents want the title of custody for no other reason than control. They think if they have custody, they can determine if their child sees the other parent and when. This is not the truth either. Having custody of your child is not the opportunity to control them. Children need both parents. Think about your children, what they want, and how to ensure that you can both be a part of their lives.
You have to work through a schedule of where your children spend the week, weekends, holidays and summer. You have to figure out who is going to pay for things like braces and sports. You have to decide who will claim each child on their taxes. Finally, you have to make desicions about child support.
None of these decisions are easy. Again, if you cannot work all the way through it, stop and try again later. It is much easier for you, your child's parent, to reach an agreement that works for your family. The big risk of not reaching an agreement, other than the enormous financial cost of a custody case, is that a judge is going to rule on every aspect of your parenting decisions. They decide who has them Christmas morning, who takes them to school, and what time your children arrive at your home.