A tank, a tank top with a light, filter , gravel, water. it could cost from 50 dollars to 5000 dollars. but if its for two fish get a 10 gallon its about 100 dollars
You need a filter, lightning, a tank, gravel, fish food, and a heater if it's not goldfish. You need to run those things for about two weeks and they cost about 150.00 in total if you buy a 10 gallon.