Upgrading a iMac G4 ?

Hi guys, I'm new to this forum and I'm a huge noob about Mac

I want to buy a Mac to compose music on GarageBand and stuff like that but I don't want to pay a lot. I just saw someone selling his iMac G4 (sunflower edition) for 80 bucks. Sounds good or not ?
Also, I would like to upgrade it to have a faster processor, more RAM, better sound card, install the new version of iOS etc. Would it be too expensive considering that it's just a G4 ?

Thanks !

You can't replace the sound card. I don't know that the CPU can be replaced. If it can, you won't see much in the way of performance gains, especially by today's standards. The max RAM is 1 GB. Macs don't run iOS. They run Mac OS X, and from what I can find out, the last version that iMac can run is OS 10.4 (Tiger). Even if that is incorrect, being PPC hardware means there is absolutely no chance it can run anything newer than 10.5 (Leopard). Mac OS 10.6 (Snow Leopard) and 10.7 (Lion) can only run on Intel-baed Macs, and even Lion won't run on the very early models of Intel-based Macs.

Eighty bucks is simply too dear alas. Consider buying an Intel Core 2 Duo iMac.

How far you can upgrade them is determined by the processor speed. The 700 and 800MHz models are upgradeable to 1GB of ram and Mac OS X 10.4 "Tiger". The 1GHz and faster models are upgradeable to 2GB of ram and OS X 10.5 "Leopard"

The processor is un-upgradeable in every iMac G4 as the processor is fused to the logic board. The sound card is also unable to be upgraded.