I am speaking as a former foster child. I was in two foster homes, starting at age 8. My foster parents are my parents still, to this day. They, obviously, made a huge impact on my life.
My parents specialized in taking in sexually and physically abused teenagers so, yes, everyone dame in with HUGE issues. My younger sisters are adopted from Korea, so all the foster kids were older than they were all the time. I think older was better. It's hard when the youngest loses there status. Every kid wants a big brother or sister, and my little sisters had them in abundance, so they could pick their favorites.
I applaud you for taking on foster kids and being a working mom. I always thought that I would take in foster kids, but I can't imagine trying to juggle that with my own kids, their activities, my job and my own activities. I couldn't do it. (Instead I choose to work with at-risk youth as a teacher, and I just don't keep them in my home.)