I also quit my full-time job to stay home and parent my foster kids. We moved at the same time, so it was "easy", I just did not look for a new job when we moved.
We have always had at least one child who is not yet school-aged and wanted them to have some consistency with one primary caregiver. Though our income has been cut more than in half (AHHH!!), we make it work and I love taking care of my kiddos. As a side note, with my current two kiddos, one is medically fragile and requires a stay-at-home parent, so we are a really good fit for him for now
I don't regret my decision for a minute. I have the best "job" in the world. And, as it says on my fridge "All mothers are working mothers".
And, as another poster said... I have never worked so hard in my life - and I thought my 50 hour weeks were stressful!