You could choose to become an employee, employer or private contractor.
As an employee, you would need to look for an employer to hire you as a virtual assistant. You would be doing tasks that are similar to what you would do in the office, but from home. Here then, you would need to meet deadlines and quality standards as any other employee would be expected to.
There is really no limit to what you can do or how many employers you can have. The key is meeting deadlines. How you find these employers is a matter of search but a good place to start is freelance sites.
Option two: As an employer or business person. This is a lot more complicated and probably more expensive to start. You need to come up with an idea to sell your own products or services and build your online presence. It does not really have to cost the moon but you need to be quite knowledgeable around the web or have the finance to hire someone who is.
As a contractor, you would be selling other people's services and products. This is what is called affiliate marketing. It is the easiest and cheapest to start and your earnings are based on your efforts. In most cases, you earn a commission on sales.
A good place to start is Clickbank. However, remember that you would need appropriate skills to start off successfully. Online coaches can help you on how to start out.