How is child support determined in Ohio?

I need to know what a judge will consider when they set a child support amount in my case. I’m self-employed and don’t get a W-2 to prove my income. I make a decent income from my business but I also have a lot of expenses, so I don’t actually take home the total amount I receive from my customers every month. How will my income be determined for a child support calculation? What documents will I have to show the court to prove my monthly business expenses, and will the fact that I have another child that I am paying support for be taken into account?