it's okay, i've been looking around online and i can get a 5 gal for like $50-60. i havent checked the local pet store though, the usually have good deals on tank kits and i know a guy that works there so maybe i can get a good deal :)
My local petco has tank kits and there is a sale right now for a 10g it is $40, for 20g it is $69.99, and for a 55g it is only $159 so check that out if you want a good deal. If they dont have that sale going on they normally have a 10g tank kit for about $50-60. Or you can check craigslist.
A heater isn't necessary right now as long as the water can be maintained at 78-80 degrees without fluctuation. For me, in a couple of my tanks, the hood light gives off enough heater for now.
Winter is a different story though.
I live in GA and I don't use a heater. It never falls below 78 unless it's nighttime, then it goes down to about 76 or so. So I don't use one. I'll probably pick one up in winter though, depends on how warm we'll keep the house.