I'm waiting for my girlfriend to be ready for a house in about 3 years and we'll have one!
Just to back you up a bit, I'm only 21. Although I'm not buying an S3 but a reasonably specc'd new A3 so it's not too different (besides clearly insurance costs). However, I've factored the price of the car/monthly repayments into my saving plan and I still come out with a fair chunk of money at the end of the month to put towards a house. At the end of the day, if you can afford it - have enough to save for a house/pay a mortgage and aren't silly with buying things for the sake of buying - this took a while to master a bit of self control, then it's affordable!
So long as you're sensible and work it all out before you buy it then I don't really see why not!