Determining Age you wish to foster?

I'm curious... How did you guys all determine the age range for your fostering license? What is the determining factor?Hubby called and said he called the Idaho supervisor and asked to back away from our pursuit of our Niece in FC there. She seems very happy and the foster family wishes to adopt her so we know she'll be fine there. She has been there awhile and is bonded also. We want what is best for her. We are going to visit her in a couple months also :) So now we're going to switch our license from specifically geared towards her to fostering to adopt kids here where we live. So we get to decide the ages and I'm curious how you guys determined that? Thanks!