Like the folks above, there isn't a specific degree, certification or prerequisite to using this site as a sitter, aside from being 18. You will find all types of people on this site offering their services: some are extremely experienced and have been doing this for years, others have only worked with animals in a medical setting and not pet sitting, others have zero experience aside from owning or loving dogs themselves. I think being 18 is the only real requirement.
Like Laura R. said, there are many things that you will learn about what you like and don't like, as well as what you can tolerate in a furry guest in your home (or in their own home). That said, this line of work probably isn't for everyone - and I would recommend not quitting your job to do Rover right away. While there are some people that can absolutely live off of their Rover funds and make a living that way, I don't know that any one type of experience on Rover is "typical" - and much like any other service, there are great months where business is booming and others that you might not even get a request.
There are many things that help Rover sitters be more successful: e.g., having patience with new dogs that might be suffering from separation anxiety while their parents are away, handling the cold well while they wait for their guest pup to go potty, knowing the right questions to ask at a meet and greet (if they even do them at all, as some don't).
As for me, I quickly learned that I loved this line of work. I do have a career outside of Rover, but as my boyfriend said, "it's great that you get paid to do something you would probably do for free!". If you are interested, your best bet will be to take the plunge: join & offer your services. You'll learn most of it as you go along, and that's also probably the best way to figure out if this is for you!
Best of luck with all of your future endeavors!