Lots of good advice above. If the location in your post is correct (Illinois) you are going to be limited as to the number of kids you can have as your own children count against the total allowed which will affect your bottom line. See:
https://www.illinois.gov/dcfs/aboutu.../Rules_406.pdf
These are the rules for regular daycare homes, not large group homes (they have different rules). Section 406.13 outlines the various limitations.