How can I find my birthfather without having to pay?

Finding your bio father will involve a lot of footwork and paperwork which I can't imagine not involving money at some time or other. Nothing is free these days.

I know my birth fathers name,and he was married to my my before I was born. Somehow something went wrong and he left when I was born.How can I find him?This was nearly 50 years ago,Ihave been loooking for at least 10 years,Please someone help me.