May be you have enough money to rent Vienna's symphonic orchestra, but in most of cases you will not have more than the money necessary to buy a new computer or soundcard. Well, don't panic mate! you don't need more than these to get some aceptable results.
The only thing you need to begin working is yourself. I'll explain this later deeply, but for the moment I suppose you have this hardware: yourself. If you haven't, ask your girlfriend, boss or teacher to have more free time :-)
2nd: A computer. You won't need a high-end one, with 4 GB RAM or the latest processor, motherboard or soundcard. Any modern computer will do this job very well.
In my opinion, and being very simple, any computer with 2 years or less will do a great job, with 2 to 4 years will do a decent job, and with more than 4 years will need extra hardware to accomplish the objetive. That is, to use an external sampler, etc.
If you're going to use your computer as sampler, secuencer and mixer the most important feature will be the RAM. Depending the amount of samples you use, you'll need a lot of RAM. To have 1GB or more will be a good idea, if you can afford it. And if it's fast better than if it isn't, of course ;-)
To have a good hard disk is very important too. Today you can buy cheap fast hard disks with hundreds of GB. If you are going to use samples you'll need a lot of disk space to store them.
Some of this SATA hard disk will have some clipping problems due hardware configuration. If you're going to use these hard disks to create music you can find more information about this problem HERE.
3rd: The soundcard. It's part of the computer, I know, but I've used a new bullet for it because it's the final interface between your computer and you.
You don't need to spend a lot of money in your soundcard, but you need to know that if you have a bad soundcard your processor will need to work harder than if you have a newer/more professional soundcard.
I don't like builtin soundcards, so any hardware acelerator soundcard as Creative SB Live! or newer soundcard or equivalent will be a better option. In the other hand, some of the newest models as the new Creative's X-Fi series, or other professional soundcards can give you extra features, but you will get good results with this cheap hardware anyway.
4h: A MIDI keyboard, controller or any other MIDI device. You can use it to play or edit easily the music you record. Of course, you don't need a MIDI device to create the music, you can write the score directly in the score screen, piano roll or other edit screen of your secuencer program, but for those of you who don't know a lot of music theory the easiest way will be to use one of these MIDI instruments.
The cheapest option is a MIDI keyboard controller. This is a piano keyboard which can't play any sound by itself. You need to connect it to your PC or other MIDI device capable to generate sound from samples, etc. You can find this from 100€/$. In the other hand, if you have a MIDI keyboard you can use its builtin soundbank to generate the sound. This is the best option if you have an old computer which can't handle a lot of samples by itself.
Ok, these will be the basic hardware. Of course, you can add as much hardware as you can afford, and probably if will help you to get better results. But may be not. Take in mind the most important hardware to get a good song is YOU.
You can have rack of digital effects, a 3000€ computer, a 64 tracks mixer or the latest Akai keyboard, but without a good idea you won't get a good song, dude ;-)
See you in the next chapter: Tools part 2 - Software