Freelancing in foreign countries and work visas

I'm wondering about the rules regarding work visas for people living in foreign countries and freelancing. I assume that if you freelance for clients in that country, you need a work visa. However, do you need a work visa if you freelance for clients outside the country you're living in?

I'm thinking this also varies from country to country. I don't have a college degree, so I imagine that would make it harder for me to get a work visa if I wanted to live in a foreign country and freelance.

Thanks for any advice.