some good posts on this, as entwisi says, do yer homework, the simple anology i used when i started way back was borrow no more than £4000 over 15 yrs, that equated to payments of £48 per month, which if the worst happened n i was cast on the dole, i reasoned we could still afford £12 per week. ok i started with a 2 up 2 down terrace, but always payed mortgage off before 15 yrs, n sold then bought a better house, using same criteria. had some lovely property inc semis, bungalow, etc, trouble today is most want the best NOW, n many come unstuck, when things like this happen.
other circs can balls things up, but that was my general rule.