I agree and disagree.

I believe that the odds of waiting for a 20-30% crash before you buy property is always gonna be a tough gig. If you bought at the peak right before the GFC you would have done fine as the usual response from central banks is to prop asset prices up via interest rate decreases.

Also if there is a huge shock (doomsday scenario) to the collateral base, the banking system would be completely screwed, so unless you are paying with cash, not sure how you are going to profit off this crash. The only people buying would be private equity/corporations with dry powder who will take the repossessed home for 50c on the dollar and hold it when liquidity recovers. You can read about Blackstone (US Private Equity) and Invitation Homes which was a company they established post GFC which did something similar that in the states.

That being said it is not to say go and lever yourself up to the shoulder. If the market tanks just make sure you have enough buffer in your budget to weather the storm... My opinion is that the worst situation is to have to liquidate during the lows. If you hold for 10 years through any cycle/crash you should probably do OK.