Real Estate Law USA.com

i started doing some sub contract work for a realtor in illinois. it requires everything from changing locks, repairs, repo work to evictions. the realtor requires that i give them 20% of what ever i invoice the job for. these houses are owned by mortage companys and they pay the invoices to her and she pays me after deducting her 20%. my question is this a legal referel / kickback or illigal?