I do it, from the US & Europe to Japan. Not going to say what exactly as I have a pretty good run on a niche market at the moment. Only customs issue I have is 8% consumption tax in Japan as what I sell is otherwise duty free. On average I can make an extra $50-70k a year in addition to my regular income, so I suppose if someone actually wanted to they could do it full time. It definitely provides me with travel money plus some, so if it's something that interests you, I'd recommended finding something fairly niche with a high margin in the country you'd be selling in, that way you don't deal with so much volume. Also very helpful to do duty free goods or very low duty.