If you write your own custody agreement and get it notarized, is it legal?
Is a document that someone printed on there computer and is signed by a notary a legal document. Like a custody document that I had signed.
Generally speaking, a notory actually adds little to the authenticity of a document. For example, contracts and promissory notes do not need to be notarized, just signed by the parties involved. And wills and trusts have their own special requirements for how sign and witness them to give them effect.
I do not believe that child custody can be determined by a simple notarized document, since courts (correctly) put the child's rights and best interests first and impose various requirements on changing legal custody. Custody is also very fact-specific. If you have a question about child custody, you should consult with local family or matrimonial attorney (if you can't afford one, try legal aid for a referal), with whom you can share in confidence all the facts of the case, including the document you are referring to.
A document that has all the elements of a written contract and is signed by both parties is enforceable, as long as it complies with the law and it is not against public policy.
Also, most states would prefer that the parties agree to custody issues and uphold an agreement. Child support is set by statute.
If you signed something that you are now regretting and without attorney representation I would get your self to an attorney right away. I would tell the attorney the whole story around why you signed it and let him or her tell you if there is any way to set the document aside. Good luck.