Fish are totally easy to take care of nowadays. When I was a kid technology stunk and nothing worked very well, but now it's easy. I got a beautiful 20-gallon setup last year for my apartment. Here's what you need:
1. Tank/stand/lid/light (you can usually get this as a combo; mine was about $100 for a nice wood setup)
2. Gravel (pick a color, you'll need a few bags)
3. Filter pump (look for Penguin filters with the Bio-Wheel) with spare filters
4. Bubble-maker (pump and bubble wand or bubble toy)
5. Heater (if you want anything other than goldfish)
6. Misc. tank decorations (statues, blue background, rocks, etc.)
7. Fish/fish food/small net
8. Water conditioner (First Step works great)
9. Sponge-on-a-stick, gravel hose, and bucket
Wow, that sounds like a lot more stuff than I had in mind. You can also add a UPS for short-term battery backup; I happened to have one lying around that I used. It's really not all that much maintenance; we feed the fish once a day and clean the tank once a month. The more sunlight it gets the more algae will grow. Once a month, I replace the filter (lift up lid, pull out old filter and trash it, slide new filter in), use the scrubbie to clean the algae off the sides, and do a 25% water change with the gravel hose and bucket (the gravel hose cleans the poop off the rocks and empties the water into the bucket; you then refill the tank and add some of that water conditioner to clean out the cholorine in the new water). That's it, it takes 20 minutes max. That's nearly zero maintenance, your house doesn't stink, you don't have critters running around, and the sound is soothing. If you have a heater in the tank, you can get an algae eater to clean off the sides of the tank for you. We have fancy goldfish (i.e. funky-looking eyeballs and big wavy tales), so we don't have a heater or an algae eater.
There are more little tricks and stuff, let me know if you want to go this direction and I'll provide more information