General knowledge, that I don't mind helping with that but things that I've learnt through lots of trial and error or experience which sometimes have cost time and money, sorry.
If the person has been doing the job for a while, then to a degree that's fair enough but when someone wants to know how to start up, how to get customers, how to do this, that and the other, then nope. What type of business help a potential competitor know how to make money?
Also, I don't see why someone should get the benefits of any of my experience for free.