Well, at its most basic level:
some recording software, a sound card, some form of monitoring system.

You can spend as much or as little as you like and the relationship between "net end quality" and "money spent" is not always linear.....

but lots of cash helps.

Excluding instruments, the computer and the DAW, I have spent about $10K on recording kit. It is a very nice system however, given an unlimited budget, I could happliy spend another 20 in about 5 min !

However you can start with a soundblaster a metronome, a guitar and a cable

or a Tascam 424 mk III which was where I started !