First, you asked about free assistance. As you can probably imagine, the demand for free legal assistance greatly exceeds the availability of free legal assistance . Finding a free attorney can sometimes be like finding a free auto mechanic, but a lot of people enter the profession to help people and can offer services at a reduced price, or can even do the work for free they are sympathetic to the case. I would refer your son here: http://apps.americanbar.org/legalservices/probono/directory/michigan.html

This organization offers a free legal clinic, and they can use their network to see if anyone might be willing to facilitate your son's case on a no-cost or low-cost basis.

Getting back to your original question, it is a shame when a parent believes that they call all of the shots, but the fact is that the law does not perceive either parent as having an inherently superior bargaining position with regard to deciding custody of a child. Custody is awarded based on the best interests of the child, and there is a legal presumption that a child's best interests are met when it has significant and meaningful contact with both parents. Significant and meaningful contact does not necessarily mean a 50/50 split, but it means regular and frequent unsupervised contact unless there is an compelling reason to not allow for that contact (for example, if one parent has a history of abusing the child).

In that context, when the decision has been made that court action is necessary, the parent interested in getting the custody order would contact the domestic relations/family law division in the county where the child resides and request a "child custody forms packet". The forms packet contains all of the basic forms that may be needed, including a petition to establish custody, a "uniform child custody jurisdiction and enforcement act" (UCCJEA) form, and financial information forms (because the court usually makes a child support determination along with custody). The forms would be completed, filed, served on the other parent, and the case would proceed from there. The parents would have an opportunity to participate in court mediation, and if full resolution can still not be met, a judge experienced in parenting issues would make the final determination on any outstanding matters.

Whether you can handle it yourself without the assistance of legal counsel depends on you. The family courts have gone to great lengths to make themselves more accessible to the public. They have partially succeeded--things are nothing like they were 30 years ago, but the process is not at all intuitive. Handling your own case is like preparing your own income tax returns; some people will always need professional assistance, some people are sophisticated enough to handle their own matter, but the majority of people can stumble through their own issues successfully as long as there is nothing unusually complex about their case. If your funds are low, I would recommend that you nonetheless consult with an attorney for an hour or two to help you organize your initial filings so you can at least start off on the right foot.