Section 274 felonies under the federal Immigration and Nationality Act, INA 274A(a)(1)(A):
A person (including a group of persons, business, organization, or local government) commits a federal felony when she or he:
assists an alien s/he should reasonably know is illegally in the U.S. or who lacks employment authorization, by transporting, sheltering, or assisting him or her to obtain employment, or
encourages that alien to remain in the U.S. by referring him or her to an employer or by acting as employer or agent for an employer in any way, or
knowingly assists illegal aliens due to personal convictions.
Since you know this person is an illegal immigrant, this applies to you. The loophole often referenced in popular media regarding independent contractors has to do with the lack of an official document requirement for hiring contractors and not knowing they are illegal immigrants. But since you already know this person is an illegal immigrant, the above applies to you. Asking this question on onstartups also means there's no plausible deniability.