How much would this cost? concrete slab porch sinking...?

I have an issue with my home. I have a concrete slab porch with wrought iron railings going up that are attached to the overhang. The concrete slab part is sinking. It's a small area but it is sinking on one side. Is this an expensive fix? Can anyone give me a ball park estimate who is either a professional or has had this issue before? Thanks in advance!