my 4 tanks are all trade me do-up's, and I say that because the cheapest way to get a tank on trade me is to buy a tank which has no frill's otherwise the sellers seem to get some crazy ideas on what the tank is worth.
But as others have said heaters, filters and other items that fish’s lives depend on are best to be brought new!
P.S don't buy a fish because its cheap as you will be stuck with it for as long as it lives, Wait and buy what you want.