I run a company that started off selling SEO services, but now I'm about to really widen my remit, not least in actual management of websites, and also installing/admin/management of forums.
The big key to earning online is to spread your risk via different income streams. For example, my AdSense revenue is now just over a third of what it was over a year ago. Individual online revenue streams cannot be relied on in themselves for the long term.
2c, hope that helps.