Do you need special certification?
That depends on your field. Some professions may require that you are specially licensed or certified, such as in real estate, fundraising, accounting, or financial planning. In addition, certain special designations may give you a leg up over competition even if the field itself doesn't actually require it.
Before you take on consulting jobs, you'll still need a ''9-to-5'' for at least a while
In almost all consultant careers, you'll still need to have a ''pre-career'' in your chosen field where you work under someone in a sort of apprenticeship, 9-to-5 position before you can hang out your own shingle as your own consultant, just to learn the ropes.
You may be able to set up the simplest of businesses, or you may need to incorporate
In many cases, consulting jobs don't require that you incorporate or do anything special in regard to business establishment; you simply establish yourself as a sole proprietor and begin to do jobs, making sure that you carefully keep track of expenses, taxes, and so on so that the IRS or someone else doesn't come after you for monies you owe.
It also doesn't have to cost a lot to get consulting job; the Internet has made it easy (once you have got the proper certifications and legal paperwork required, depending on your field) to advertise and get work — and of course, you can also depend on previous employers to get clients if they'll refer them to you, for example. You may need a website, and you may need to advertise somewhat, so you'll have those expenses. You may need permits or special licensure to practice in your particular area of expertise. That said, though, most of the time, it doesn't have to cost a lot to become a consultant.
Is it for you?
No one else can tell you whether or not being a consultant is right for you. There are certain things that need to be true about you, though, to make sure that you'll do a good job as a consultant.
There are a lot of benefits to being a consultant, of course, but there are also some drawbacks that may not be worth it for you. For example, your hours are probably not going to be regular, you're going to have to have a lot of self-discipline so that you will work even when you don't feel like doing it (and even though no one else is telling you to go to work), and chances are, you won't make a lot of money in the beginning and may have to struggle a bit. Even when business is good, you may not have a steady paycheck.
So if security and regularity are of paramount concern for you, being consulting jobs may not be right for you. And if you don't have the self-discipline to work even when you don't feel like doing it (and even though you don't have someone cracking the whip over your head to go to work), being a consultant is probably not for you.
However, if you're very self-motivated, you love the freedom of setting your own hours and not having anyone tell you what to do, AND you have the discipline to keep going even when the going gets tough, consultant careers may just be something you'll want to consider. First, of course, you'll probably have to put in at least a little 9-to-5 work to learn your particular field, but then after that, there are lots of consulting jobs out there just waiting for you to take them — if you want them.