Ask HN: Employer obligations hiring an international (in the STEM OPT program?)

I run a small business and have the opportunity to hire an acquaintance for some work while being able to help keep them in the US. I'd get smart-but-not-fully-relevant labor for cheap and help them stay in the US.

I figured the HN crowd has a strong contingent of people running businesses hiring internationals, so before I consult an immigration attorney I wanted to check and see if there was any red flags or advice HN could give. Anybody previously run into this situation have any tips?