Hey
First of all welcome to TalkFreelance.com
Your goal of $100 per week is reachable and you could easily do this with a few easy steps to getting yourself known for what you're good at.
Speaking from experience, I'd say it would be good to:
1) Take on a few projects for FREE (I'll explain)
You want to take on a few free projects not just to start your portfolio but also it gives you the opportunity to deal with clients and their demands. You may have done this before, but if it was a while ago, times change and clients only get more and more demanding.
You want to take on some small projects for free and agree a free based verbal contract so they're not making you work all hours of the day and night for nothing, but you want to remain professional and show the client you're capable.
Taking on free work usually, in some cases lead to further paid work by them on that project, or another one of their projects or from somebody they have referred you to.
2) Build yourself a portfolio of work
After completing a few free projects it gives you a great step into getting started with your own portfolio. Create a basic page that shows the work you have done and the features of the work.
You say you're a programmer so outline the programming technologies used and what features the application has, even the small features. Programming takes time and effort, and if there has been effort given to the project, it will shine through in your work, writing and presentation of your website.
Make sure your portfolio really informs people what you're capable. Don't try to move too fast and make sales with this portfolio. The portfolio should act just as a portfolio of you right now and what you have done.
The portfolio will give you more chance of being noticed and be able to target people in need of programming work on forums and websites for these types of requests.
3) Start selling yourself
By the time you've built up a good portfolio you want to begin letting your website make sales for you. In conjunction with your portfolio you want to outline somewhere on the site in a separate section what you can do. List anything and everything you can do for the client, the more technologies you can integrate with what you know and making sure you're capable of doing all the latest in programming.
You may want to choose a hourly wage or quote per project, but you want to let your customers know how much they can hire your expertise and time for to develop something they cannot do. Often clients come to me who will complain because of quotes I have given them. The important rule to earning that $100 per week is not to accept small jobs for $10 which may take you half the week doing and taking on 10 at a time, but to offer your services for a price that is in competition with everybody else and that is appropriate for your talent. The client wouldn't be hiring you if they knew how to do it, had the time to do what they need you to do or weren't interested in your work.
Once you've got a site up and running and your work on display, and clients will start to mount up.
Make sure you know what you're doing per project/client and set deadlines. You may only need to work one project per month to meet your $400 goal so make sure you do work for a price you deserve.
All the best with your website