You can purchase one now, but it is a dev kit, ie meant for developers.
Inside it has a samasung galaxy s3 screen, which has a high resolution of 1920 x1080, but when stuck close to your face with the magnifying lens it does show individual pixels, ie a "screen door" effect.
The near consumer version which oculus has been demoing, has a much higher res screen which gets rid of the screen door, and various other technologies to help stop motion sickness .
A reasonably grunty computer graphics card is required as you have to achieve 75fps to prevent motion sickness, which works well, older demos not running at this instantly gave the vomit inducing feeling, but now
everyone seems to have optimized there programs and games so they run at 75fps, i think the consumer is aiming for 90fps.
So you could go buy this now, but i personally would wait, they have said it will be out in months not years.
Samsung has just released the samsung gear, with which you plug in your galaxy s4, this gives you a mobile experience but only runs at 60fps, so motion sickness can kick in.
This is just the tip of the vr iceberg thats coming, you wait in 5 years time vr will be everywhere, fun times if not abused