You are better off getting a used tank on craigslist. I have seen tanks that have a hood,heater,filter for really cheap a complete set up even with gravel. I've even seen whole tank set ups with fish included. If you do not like the fish that comes with the tank rehome them or get credit at a local fish store or sell them on craigslist or give them away. Craigslist is great. I got a 30 gal. Bowfront tank with a nice black stand had gravel,background and lighted hood for $70.
I switched out the gravel and sold it at my fish club, sold the background also= from the price I payed for the tank. I used pool flter sand from my 55 gal. tank that I took down as I downsized. I sold my 55 gal. with heater,stand background, hood w/light, Bio 4 cartidge filter + filter media for $125 complete to aunt kymmie's friend that was looking for a 55 gal. tank.
If you get the $ a gal. it adds up on a hood,filter,heater,gravel and will exceed the cost of tanks that you can get for cheap on craigslist. I have seen salt water tank setups go really cheap also with live rock on craigslist. It's easier to get a setup already started and running. People move or get out of the hobby and just want to sell their setups then to move them. look under the Pet,General for sale section and the free section on craigslist for your area where you live. I do see free tanks sometimes and fish for free. But I check everyday for aquarium stuff.