Is Offering a Finder's Fee Illegal?

[Hal Cranmer]

I am thinking of ordering some business cards and get into wholesaling. I have flipped and rented out several properties and wanted to do some wholesaling to

a. Find some good properties to rent/flip

b. Make some extra cash for rentals and flips

Everything I read says offer a finder's fee on your business card for people to bring you leads. But I heard that these fees can be illegal. Can I put that on a business card and leave them around? Or will it get me in trouble? I'm in Minnesota if anyone has any local knowledge. Thanks.