My fiancé has a 3 year-old son who has lived with us on a full-time basis for over a year now. His mother has just recently begun to get involved in his life, after having to deal with some personal issues. She is financially and emotionally unable to care for her son, and has given my fiancé and myself verbal custody of him. We have had no reason for any written agreements regarding this matter until now. The mother and I both need a document stating the custody arrangements of the boy, and we also need a document starting the custody arrangement of him in order to register him for school. We have been told that they need to be legal documents, and cannot just be verbal agreements. With that said, we all get along great. There are no disputes, and his mother even spends time at our home, and attends events with us as a family. We do not want to go to court, and we don't have a lot of money to get an agreement drafted up by a lawyer (we've been quoted $800.00). Is there any other way of having some sort of legal document drafted up stating that my fiancé and myself have sole custody of him, that she can have access to him whenever she'd like (as long as he doesn't already have plans), and that his primary home is with us?

No, there is no way to do a do-it-yourself document to safeguard these arrangements.

You need an Attorney if the arrangement is to be legal.