While it seems like a great idea to buy that gorgeous fish from an online auction/store, one thing to consider before doing so is the health of the fish. While most people have great fish sometimes the pictures they show aren't real. Look for a return policy in case the fish arrive at your door dead or sick. Most, but not all, sellers will have a return policy that consists of sending them a picture of the fish, still in the bag, to show it's expired. I actually came across one that wanted the picture within an hour of you receiving it. So, check the return policy and if you're comfortable with it, check shipping prices. Most sellers will ship overnight, some by Priority, depending on the fish itself.

Also, make sure you have done research on the fish you're looking at. Tank size, any special requirments, type of food, filter for tank, heater, etc. Also, make sure your tank is big enough for the fish when it's reached its full size. A lot of people are under the assumption that you can put 10 Goldfish in a 10 gallon tank and they will live happily ever after. Not true. Your Golden Pal (specially depending on the breed, i.e. fantail) is going to need a lot of room for just 1. Rule of thumb, 1 goldfish for every 10 gallons, 15 gallons would be better, 20 gallons would be perfect as Goldfish produce alot of waste.

Consider buying live plants for your fishy friends while you're at it. But, make sure you have all the info for the plants you're looking for as the tank will need special lights. Some plants require a ton of light while others can thrive in the dark. If you plan to breed any fish, make sure you have the right plants for the babies to hide in. Always make sure the fish and plants you buy are able to live together. Some fish will dine on your plants while other fish will only eat the plants if they aren't fed enough fish food.