No matter what your agreement says. Child support and custody can be changed. For example, you can't waive child support in return for custody. If the noncustodial parent is unemployed, the court reserves the right to award child support at some time in the future -- or even award child support based on what that parent could be earning, if it looks like the parent is voluntarily unemployed. And even if a husband and wife agree that the husband will have sole legal custody, the wife can always ask the court to change that arrangement later on, if it can be shown that the change would be in the child's best interest.(Incidentally, if you refuse to allow the other parent to visit a child, you could lose custody -- that refusal is considered a change in circumstances that might justify a change.)
Remember, too, that only a court has the power to modify an agreement once it becomes part of a final decree. Let's say you're supposed to pay $500 per month in child support, but then you take an early out from, say the Navy, and you can't find work right away. Your ex says not to worry -- she'll accept $100 a month while you're living on unemployment. So for six months you give her $100 per, and then when you get a job paying $500 again. She can sue you for $2400 ($500 - $100 = $400 x 6 months = $2400), and she'll win. Even if she gave you a written, notarized statement that she'd accept $100, you still owe her the difference.
The moral: If you're paying support under a court order, and it's more than you can afford, ask the court to change it.
It's only a private contract. A separation agreement is indeed a binding contract, but until it becomes part of a divorce decree, it's only a contract. That means that if someone is supposed to be paying support and doesn't, you can't get his or her employer to pay you directly. Instead, you'll have to sue the other person on the contract, just as though you were a landlord whose tenant hadn't paid the rent. And if you win, you may have to jump through some more legal hoops to collect.
You're still legally married. People often refer to a separation agreement as a "legal separation." It isn't. Many agreements contain language that allows both parties to "live apart as though unmarried" but that doesn't necessarily mean you can move in with your new sweetie. Unless your agreement also says that neither one of you will seek a fault-based divorce, you can still be sued for divorce on the basis of adultery, even if it happened after you separated from your spouse.
You can't have everything. If you get everything under an agreement and he gets nothing, and especially if he didn't get the chance to talk with an attorney before he signed, he might convince a court that the agreement is invalid.Note that a completely one-sided agreement is probably unfair (so that a court could refuse to accept it) but a merely lopsided agreement might be okay.
Finally, even though you and your spouse are in complete agreement on everything, an attorney can represent only one of you. If there are any points that a couple hasn't completely resolved, the client is the person in whose favor the attorney will draw the agreement. If your wife has asked an attorney to draw up "your" separation agreement -- that is, the one you and she wrote down last night on a piece of notebook paper -- be sure to have your own attorney review it before you sign.