It makes me really upset when people say things like "oh I had a goldfish live such and such years in just a bowl".
And my answer to that is: Your goldfish didn't live, it just existed.  A good analogy to that would be if you kept your large pet dog in a closet.  Would he be happy?  No! he would be forced to live in inadequate living conditions!
A goldfish can grow up to 12 inches.  It needs room to swim.  It is not able to breathe oxygen from the air.  It's only source of oxygen is from what you provide in it's home.  A goldfish takes in oxygen only from the water it lives in, through it's gills.  Your mom's goldfish might have lived 30 years or more if it had had a different living environment.  At seven years it should have been at the prime of it's life.  IMO it's life was cut short by inadequate living conditions.
And no a jar isn't a good place to house a goldfish either!  You have to have good surface air exchange.  A jar is too narow at the top.  You want somethig like an aquarium that is longer than it is taller for good air exchange.

Don't buy a goldfish, buy a betta instead.  A betta is pretty and it can breathe oxygen from the air.  A goldfish cannot.  You will see your goldfish hanging and gulping for air at the top of the bowl and that means it is suffocating!  A betta if it doesn't have enough oxygen in it's water can go to the top and take a breath at least.

Yes, please buy a betta.  Goldfish grow quite large despite their container.  Keeping a goldie in a bowl is like trying to keep a german shepherd in a puppy crate for the rest of its life.  Goldfish can go blind and get brain damage from living in too small of a container, and they suffer horribly before they die.  Bettas, on the other hand, come in beautiful colors, love living in a bowl, are easy to care for, and have a lot of cool tank decorations.  Check out Google Images for pictures of bettas and betta bowls.  They're really popular nowadays.  They can certainly live in a jar.  Besides, if you did have a big tank and wanted to get a goldie, you would have to wait two weeks for the tank to cycle to keep the fish healty.  With bettas, all you do is buy a bowl and your fun decorations, some food, and a plastic bottle of betta water, and you are good to go.  Oh, and do remember to feed your finned friend this time!

must agree with everyone else here.

i love the fact that you really want fish and are being sensible enough to come here and chat to everyone, but as the other said (and i agree) i think you should wait a while (if your heart is set on some goldies or fancys) if your just looking for a nice fish that isnt as much work, as the others said betta are the answer. i have 6 orandas (4 of them are 5 inches and 2 are 3 inches) they have always had planty of room, food, oxygen, plants to destroy haha gravel to dig in and wake me up with. i think a bowl isnt a good place for them. as Nicole said, poor living conditions can destroy perfectly good and beautiful fish.

if i were you i'd have a serious think about how much time you have to dedicate towards them. there isnt a day that goes by when i dont check my tank, or have to do mantinence etc (and i work full time 6 days a week) it is a hard slog sometimes but it depends on how much you want it to work. i love my babies and wouldnt be without them as im sure the others would agree.

sorry for the long one there guys haha
 

OOPS! I ment 20 gallon Fish are very inportant the deserv to have a good home! I'll also buy some deco for the tank as well (Already have peebles )

I was shivering and my heart ached when I started to read through this tread... keeping a goldfish in a bowl or a JAR !!!!

But now I am happy that you're getting a 20 gal tank. Well, all was explained why our beloved goldfish MUST have all that space...

Be happy with your happy fishes and please post some pics soon

Lol I know! I'm saving up my money for a tank & some Goldfish  (Goldfish are easy to save up) & Food I'll post lots of pics

Wonderful! I'm very glad to hear that you're getting an adequate tank
Be sure to get good filtration and a little air stone too! The stones are really cheap, and the air pumps for them are usually no big bullet in the wallet either

yay were all happy haha *and all the fish are happy to*

Yeah, at least past the stage with ammonia and the worst nitrites! D:

Get yourself a water test kit and check these parameters daily, and "feed" the empty tank with some fish flakes or shrimp to get the cycle going

They're so cheap anyway that you don't save much leaving them away d: Besides, with goldfish, it's always better with a bit of extra oxygen

well everyone no fish intill December but thats completley okay! they will be here at Christmas woowho!

I'm thinking just to start with regular goldfish then move on & get more as I go

the one thing u can use is a rubber made container u can get ones that are 20 gallons

Yeah, a rubberMAID brand tub or one simular.
You can get them at Walmart etc.  They are cheap and you can hang a power filter on them.
I transport my fish in them.  The only problem would be that you wouldn't be able to see the fish very good from a side view, just from the top looking down.