That's a pretty arbitrary measure though - you're making "free" money either way to pay towards that mortgage while retaining the whole value of the asset while it is gradually purchased. Whether you've got enough to cover mortgage or not doesn't necessarily flip a binary switch making it a good investment or not.

Property ownership is a market barred from entry by a high buy in cost to account for some risk - but the risk is rather minimal and most properties are going to be value accruing over time. We can observe this by looking at how cheap general property insurance tends to be (unless you're in a really risky area - i.e. building a house in a flood plain).