Craigslist might have a good deal for you, or maybe not.
You can get a cheap starter tank kit from petco, petsmart, or walmart for about 40 bucks or maybe less, about 20 gallon or 10 gallon. Shop around for the prices, those kits usually come with a cheap filter and some kind of light hood. You can get better stuff if you buy things separately, but kits are way cheaper.
If you can get one, my Aquaclear filters have been great. They aren't very expensive as far as filters go, but a new size 20 would cost you about 30 bucks. Aquaclear size 20 would be great for a five, ten or even twenty gallon if it only has a few fish.
Since you have live plants, look for a hood that uses fluorescent bulbs, or a fluorescent strip light. A low watt fluorescent bulb is plenty for low light plants, like java ferns and anubias. What plants do you have? The ones I mentioned are way easy, even I can take care of them! A hood in one of the petsmart tank kits i bought had an incandescent hood, but i found a little ten watt fluorescent bulb at walmart that fit in it. (I'm not 100% sure if it worked like a regular fluorescent, but if it fits and lights up, it works, right?)
My best advice is shop around at your local stores and see what is available.
Beware of trying this on a budget. I started with a $25 five gallon kit from petsmart, but ended up spending a few hundred on bigger tanks and upgraded filters, decorations, plants, and medications. The fish were the cheapest things I bought. That kit was the bait, and I took it! Now I'm stuck on the boat!
You can get a decent, cheap HOB filter for as little as $8 on the first web site. I would recommend the Aqueon Quietflow to start with. Cheap, quiet, and does a nice job. The only thing is the flow rate isn't changeable like more pricy HOB's. Check Amazon for equipment too. I needed an adjustable heater quick and got one for $10 shipped. I have had it for several months and it works great. A ten gallon tank and the local Walmart runs around $13 dollars here. Lots of research and you can get some great deals. All you need to start is a tank, heater, and filter. If you want live plants you can use a cheap metal dome clamp light in the hardware department of most department stores. Runs around $8. Then buy spiral CFL daylight bulbs, 3 for $10 at walmart. I grow high and medium light plants with them. Just check the light bulb box and get ones that say 6500k. 
