I talked with my uncle 2 days ago. He said he's playing this MMO and got hooked up, so I give it a try.
Here is the main page if you want to see.
http://www.kongregate.com/games/edgebeestudios/swords-potions It has 2 versions, same trading type but different game play. IMO the first one (with link above) is more difficult than the second one, since you may get bankrupt if you are not careful. And you need a decent amount of English understanding in order to play this version because the dialogue is easy to confuse you, that's one way of trading, though I may add.
Overall it's a free-to-play (f2p) game. You don't have to pay money to play it, just your time (if you think you are very easy to get carried away I suggest use an alarm clock, just to be safe).