Legality concern

[Wade Stahle]

I have some people out of state that I am helping sell their house and they are giving me 3%. No wholesale or double closings. Basically they will just cut me a check when they close.

The whole point of this was to not use an agent. I had an agent call today that wanted to see it and then started going off on how im doing something illegal.  What is possibly illegal about this?