If you can get a miniature greenhouse, like the short ones they have for starting seeds and flowers and such, you could maybe keep a bical for a year or two in it. You'd need to get a tray to catch water at the bottom, a heater, a humidifier, and a bright water-resistant light.
You can get a little greenhouse for about $40. A storage bin can make a good water tray for $10. An aquarium heater is $12 or so, and a jar to put it in is $1-$2. A humidifier will run you from $20-$50; you can buy a 'warm mist' humidifier since you're growing a warm-loving plant, which is the cheapest kind out there, or you could go for an ultrasonic fogger, which works very well and can be found for $30 or so if you shop around. A good light for this application would be a Fluorex floodlight from Lights of America. These cost about $30, and you need to connect an appliance cord to them, which costs about $6 plus the tape and wire connectors.
So, if you can scrape together $100-$150, you can probably get a workable setup. You can take your time and just get one part at a time - I'm sure that all of your Neps would appreciate a brighter light, or higher humidity. Or you can save up and try to get your parents to pay you for some extra chores or something, and buy the whole setup at the same time when you have the cash. And if you can get your plant to work outside, you'll have the summer to put things together. If you start with a small plant, you should be OK for a year or so in the space one of those mini-greenhouses provide, but you'll have to plan on getting or building a larger enclosure in the future. You can shop the classified ads in your local newspaper for large used aquariums, or look at craigslist.com - that's a good way to find a large tank for a cheap price (or sometimes even free.)
~Joe