What is cost of divorce and custody lawyers

What did you pay what was final outcome

My brothers wife left him and their son when he was 6 months old she cheated and left because she was not happy my nephew is now 4 and just now they are talking about divorce and she wants him to keep my nephew still she just wants visitation she got a lawyer but my brother is unsure if he needs one too being a single dad he cant afford much? She seems to just want to keep things as they are but my brother wants full custody and she can see my nephew like every other weekend that's if she even picks him up which she probably wont :( they been putting it off because of the hassle but it needs to be done

I'm wondering what average costs are for that or if they can use her lawyer together