Generally speaking, a child support attorney may charge anywhere from $100 to $500 per hour. In an uncontested case, the total fees might average around $2,500 to $5,000.But, for contested cases that lead to a court battle. Legal fees could end up costing $5,000 to $25,000 and up.Depending on your situation and the child support issues(s) to be worked out, you may also want to hire a lawyer on a flat-fee basis to perform specific tasks.For example, a child support lawyer might charge $1,000 to $2,000 to do a standard support modification.It s common for lawyers to ask for a retainer fee, which is an amount of money that is paid up front and based on the expected cost of the case.egal fees could end up costing $5,000 to $25,000 and up. Depending on your situation and the child support issues(s) to be worked out, you may also want to hire a lawyer on a flat-fee basis to perform specific tasks.