Fishing is a great source of income. You can go many different places and catch many different things.
Fishing can be found at The Ocean. To start with, you need to buy a boat. After that, the basic requirements are a few buckets, a fishing rod, and some boat fuel, then you can travel to various locations (depending on your boat level), and do some fishing by selecting two co-ordinates on a mini map. Once you are done, you can sell your fish for cash. (No, you cannot eat them...) Remember, you can only go to certain places depending on the level of your boat, and you can only cast out a certain number of times daily depending on your rod level. Also, you can only take your boat out a maximum of 2 times daily, so its worth it to be able to do as much as possible before you have to head back in. You can purchase Fuel at the Fuel Depot at 100 gold each. You can purchase buckets to hold your fishes at the Bucket Shop at 5000 gold each. Good luck!