You can look into either SEM or SEO work.
Those are two avenues of helping businesses generate leads and sales online. SEM generally refers to paid ads, either on through direct searches, or display (whether through facebook, websites, etc) and SEO is the process of optimizing a website to slowly rise through the search results page rankings.
Between the two of those, PPC has a lower barrier for entry but lower pay rates. SEO is a lot more complex and you're often at the mercy of google updating its search engine, but the pay is better. If PPC is done right, you can see immediate results whereas SEO is a much slower process.
If you're interested in learning more, I can point you to a couple of resources for both.