First off I know this has been covered on SO. But the most popular posts I see date back to:
Have there been any developments on this issue since these posts? Am I still just better off trying to find a reasonably priced mac on craigslist? Is there a mac emulator that I could run on my Windows 7 machine?
as far as I know, it is not possible, at least not smoothly as you wish.
Apple will never support it, as they will never support two hardware platforms and two operating systems. More than that, they will not be able to guarantee the experience and quality of running stuff at the same level that it is on a Mac.
Another point is that they want you to use their hardware, because they know the moment you use it, you will never use Windows again (trust me, I see that happening to every single person that crossed that bridge). The experience is far superior. (you will never switch back to a VW Beetle after starting driving a Ferrari)
Obviously you will always have solutions for running stuff on Windows and make it work, but your environment will be too adapted that I don't recommend this. C'mon, for about $500 you can buy a 2008 iMac. It is not that much money.
If time is money, and you don't want to spend your time fighting with immature development tools with various limitations (especially support), then for iOS app development you should get at least a used or refurb Mac Mini (with an Intel CPU + Snow Leopard).
It is possible, t run Mac OS X on certain pc hardware. But as it not allowed by apple, and it is somewhat painfully to set it up, considering buying a mac to develop for iphone, is the best choice. The risky side however is, that you may start hateing Objective-C and that you will have wasted money on buying a Mac ;-)
Alternativly for small prupose apps, considering developing apps with the help of html5, css and javascript could be a choice. Later you can "deploy" the app over safari, by adding the site (app) to your homescreen.