Interestingly similar discussion going around in the UK at the moment after a UK MP came out saying that '£70,000' salary makes you 'rich'. 70k as a single income won't get you a flat in London in any reasonable time and you'll most certainly be renting forever on that kind if money in London. Even if its triple the average UK wage. Location means everything.
Only if you want to live in central London. You can still easily get a house on that income in London suburbs. For example you can get a 3-bed in Orpington (20 minutes by train to London Bridge) for around £400k which should be comfortably affordable to someone on 70k.
The mortgage on that will be using up around half of your income. That's insane.