It really depends on what kind of business they are consulting in regards to, and what company they are with, but on average, a business consultant should expect around $80,000 a year.
it all depends on how successful he is. if he is consulting on a big deals,deals that turn out to be profitable, then he should make a good living out of it - $150K a year.
The average salary that a business consultant makes is around 60,000. However this is depending on the years of experience and what contracts you are able to get. Some people are independent contractors and work based on various contracts.
