The average house price is now over 1 million. If you buy a house for 1 mil with a $200k deposit (unreachable for the vast majority including me) then your weekly payments are over $1200 excluding rates.
To rent a property it is very easy to find a multitude that sit at the $600 per week mark and some even lower for the same number of bedrooms.
So “If they can afford to pay you rent then they can afford to pay a mortgage” is stupid. Mortgage is literally double the cost of rent.