Or I could have said 'freelance'. Short questions tend to lead to short answers. Seriously, your question lacks some information. Where are you based? What can you code? What exactly do you know of "online marketing stuff"?
I'm assuming you're young and/or just starting out. 1K a month isn't even minimum wage where I live, so the upside is that it shouldn't be too hard.
Whether you go the job route or freelance route: showing what you have done or what you can do is often more important than formal education. Having a Github account to show off your work, a StackOverflow profile (with answers, of course), a personal blog, that kind of things.
For freelance work, look at Elance or Odesk. You can do a couple of cheaper gigs to gain experience and good reviews, after that you can go for the slightly higher paid ones.
For jobs, I'm sure there is some sort of job aggregator where you live. Or ask around your network, I got most of my jobs/gigs from people I know. Good luck!
C# is good to make money as a consultant for big corps - but if you're not on client's site - it likely be a problem.
Ask HN: Shortest path to $1 million? https://news.ycombinator.com/item?id=5885922
That's why I asked for clarification; I thought there might be a typo. I hadn't considered the possibility of location-based factors, I will admit, but OP didn't provide information on that either.