Hee! My tank came with the best accessory: a mommy.
My mom's been keeping fish for 20 years, there's pretty much nothing food/chemical/medicine-wise that she doesn't have in her cabinet under our 55 gallon downstairs. I managed to get my Betta's setup for about 40 bucks, because most of it was supplemented by my mom's supplies.
Of course...there's all that shopping to do for the upgrades.
I'll never forget the day my mom looked at her giant Pleco, Rosco, and saw that he couldn't turn around well in her 50 gallon.
Me: So...are you going to give him away? I love Rosco.
Mom: I could do that....or I could get a 99 gallon tank instead.
Mom: Who wants to go to the fish store?