Well, I hate to be a negative person on this, but it is something one really has to think about closely. I mentioned that the 'Gold Rush' with respect to ISO 9001 is 'over' because there are so many people who have been throught it if only in a company they worked in. Add to that how many people are out of work, starting an ISO 9001 consulting business is a very popular idea. Unfortunately low hanging fruit is gone.
The big money in ISO 9001 was pre-2002 (to be generous). I was lucky my self because I started about 20 years ago. But by 2002 the 'big' money was gone as far as implementations go. Big companies were already registered, for the most part, so one had to concentate on smaller 'fish' who had less money to spend and were more indignant about having to register to ISO 9001 in the first place. It is almost always done as a customer requirement. I also cite 2002 as it was the last year I did any significant work in ISO 9001. By then even auditor pay had dropped significantly. By 2002 it had become relatively low paying with constant travel. I was lucky in that I had other income sources/investments so 'dropping out' wasn't that hard on me.
I was even luckier with the old QS-9000. While TS 16949 did come along and replaced QS-9000, QS-9000 was nothing short of a bigger gold mine. However, with TS 16949 the AIAG et al tied that up through tight control of who can become auditors so that is a difficult field to break into.
As a general comment, if you want to see how tough the field is these days, look to registrars who are having more and more problems finding and keeping new clients. Growth has become a problem. When the majority of large companies are already registered, the focus has become smaller clients which, as I said, pay less and aren't always happy about it in the first place.
A similar effect can be seen with the internet. I rarely go to internet web master forums these days because most of what is discussed is essentially 'old hat'. Tens of thousands of people are starting web sites and expect to get highly ranked in search engines quickly. The internet 'Gold Rush' is essentially over as well. A friend of mine has been in contact with me about a small site he started and wants to learn how to do this 'internet stuff'. It's a site for his brother's art work. As I told him, stop by any time. I'll even spend a couple days with him if he wants to come here and spend some time. But, no matter what knowledge I impart to him it will, like most small businesses, probably not become a significant income. Luckily the investment is relatively small initially. Then again, there are people who do quite well starting up internet sites which become profitable so it's not impossible. It just isn't as easy as it was years ago. The competition is fierce.
My honest belief is that to get into consulting you have to find a niche that you are good at and enjoy. But the problem is there are few niches left. Competition, especially from big, established companies, is everywhere. Most people do not do well as individual entrepreneurs. Finding a company to work for is usually the best bet.
Just some thoughts...