Which also makes even less sense, because now instead of learning less you have to learn more. Also they cost a lot, because they are very hard to develop. In my honest opinion, if you are a hard-core i OS developer then for sure buy the best Mac and learn objective-c.
It's expensive and takes time, but if it's your path, it's worth it.
The first route requires modifying (or using a pre-modified) image of Leopard that can be installed on a regular PC.
If you purchase (or already own) a version of Leopard then this is a gray area since the Leopard EULA states you may only run it on an "Apple Labeled" machine.
As many point out if you stick an Apple sticker on your PC you're probably covered. The EULA for the workstation version of Leopard prevents it from being run under emulation and as a result there's no support in VMWare for this.
You don't need much horse power to run the SDK and you can always sell it on later if you decide to stop development or buy a better Mac.
Update: You cannot create a Mac OS X Client virtual machine for OS X 10.6 and earlier.