If you're on a tight budget, stay away from Macs. PC's are cheaper, and there's a lot more software available for PC (which is also often cheaper too). Don't believe anyone that tells you that Macs are "better" for audio (or graphics). Both have their pros and cons, and neither is more capable than the other. That said, dollar for dollar, PC's will usually outperform macs. Some just prefer one over the other, and that's cool.
What equipment you will need depends largely on what you want to record. How many instruments will you need to record at once? Acoustic instruments? Vocals? The desired quality of the finished product will determine how much you can expect to spend. If your just laying down some quick demos or projects for fun, you can probably get by pretty cheap. If you want to cut flawless, pro studio quality albums, get ready to lay down some serious cash.
There are A LOT of options out there, so first narrow down what you want to be able to do.