Goldfish have natural life span of over 20~30 years, if your goal is only a few months, it's like getting a puppy and expect it to live a few months and you will be fine with that.
No fish should be in a fishbowl. Those bowls aren't for fish keeping, it's nothing more than marketing. Fishbowls are in fact fish killers.
Goldfish is a very terrible idea for a beginner. They grow big (fancy goldfish can be up to 6", common goldfish can be over 10" long), they eat a lot, poop a lot, it means a lot of ammonia produced and ammonia is toxic to the fish themselves.
For fancy goldfish, you will need minimal 20 gallon for the first one, total 30 gallon for just two.
For common goldfish, you will need minimal 40 gallon for the first one, total 55 gallon for just two.
You must also have an adequate filter system. Without a filter, the fish will just die in a few weeks or a few months at most.
To understand the basic steps for getting ready to own a fish, you should read the following article.
http://petskeepersguide.com/fishless-cyc...gen-cycle/
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