I've been a freelance IT consultant since 1986 - programing and Systems Design. In that time I've done (and notable still do) IBM Mainframe through to Windows & Web Development.
So part 1: learn new skills.
I always made sure that I knew everything.
I did not take the specialised route. You can make far more money (eg Documentum now; SAP a few months/years back etc.) if you specialise in this month's flavour.
At the end of the day if you deliver more than your competitor (your permie colleague) and keep sweet then just a few contracts turn into a few years worth of well paid freelance work.
As you go along life, you can squander or you can save, again your choice.
I suppose if you want to retire at 40 then save.
What this really means is diversify. Buy a another business, some property, whatever.
I poured all my spare cash into well selected (by me because freelancers know that permies are a waste of a salary) stocks and double my spare earnings from about 5 years of well paid contracting. I can really retire at 40 and have great holidays etc.
Its difficult now as there are more vocationally trained graduates but they still have a lot to about cost benefit (at support or development stages).
Part 2:out do your peer! You can't compete with graduates because they work cheap, so do something different: cross platform connectivity; legacy work etc.
Earn your references: you can work on low paid jobs but if you make yourself a key person you canthen realise a good rate increase.
In a way this is a downside of freelancing: you have to be prepared to prove your worth in advance...
There are hundreds of opportunities in IT with the internet.
good luck