You can read through my answer in the link that Partha has provided. I'll elaborate on it some more –
I became a freelance writer around 10 years ago when I discovered this thing called 'ghostwriting'. I had posted a response on someone's blog and had penned a few articles, which got their attention, and they contacted me, asking me, to write for them. That was the start and I soon discovered there were many opportunities available to people like me. It was better than playing online games, which I did at that time, as I kept my daughter company, while she burned the midnight oil, studying for her 10th boards. I had felt guilty sleeping, while she studied. What started as a distraction soon became a full-fledged job, with people I worked for referring me to people they knew and me taking on more and more writing assignments.
Today I write for people I have come to know and for strangers who request work on various online portals. The major chunk of writing that I do is for them. It is mostly ghostwriting, with very few opportunities for a byline. ISC is one of the few portals that let me publish under my name.
For me writing is a profession; just as you are adept at playing musical instruments I am good at what I do. It comes with the territory, you learn things along the way, and with time and practice you hone your skills and become proficient at the job. It's true of everyone.
I have always admitted that I write for the money and every penny adds up to the kitty. However, I do not indulge in posting nonsensical posts to ensure that I make that money. Writing for ISC is not difficult as the format is known to me. Most of the material I post here is from the knowledge that I acquire through reading, my personal experiences and from watching informative television shows. It is just a matter of transferring all that into words. Contests require a wee bit of research, but the writing technique remains the same. Having a good vocabulary and grammar skills help. I have also learned to type real fast, using just two fingers, so that helps. Moreover, I usually multitask, which means I type while watching television.
"A love affair with knowledge will never end in heartbreak" - Michael Garrett Marino