The 40 gallon breeder is the smallest sized tank recommended.
It can be purchased at Petco for 50% off during their $1 per gallon sale, which runs quite a few times during the year. It can also be found used on Craigslist, but make sure to disinfect it properly before use, using diluted bleach.
Because hamsters are little escape artists, you will also need to purchase a screen cover top* and locks to secure the cover. This would cost you $20-$30. Or you can make a lid using wire mesh and wood strips.
You will also need a sturdy stand for these tanks. You can buy a stand from the pet store or use any piece of furniture that you already have that will support the tank. As tank stands are quite expensive, Ikea has some affordable options. One Lack coffee table or two Lack side tables will do the trick.
Water bottles* can be easily attached by either purchasing a metal water bottle guard, which will also protect your water bottle from chewing, or by using industrial strength Velcro* or magnets*. Other items, such as hammocks* can also be attached by using suction cups.