Keeping in mind there's a difference in mortgage amount and house price.... I would imagine most people would have at least a 10 per cent deposit. Houses in my suburb have a median price of around $550k (35km from city) so imagine average mortgages would be $450-500k.
Good point, we were chatting as owners changing over to our 4th property with a substantial amount in the bank. First home owners would be different I guess but still having a 10% deposit and starting a bit smaller.

Our first property was purchased in Bayswater for 100k about 15 years ago and sold for 260. Crazy.