China's property crash is prompting banks to offer mortgages to 70-year-olds

The us will happily give a 30 year mortgage to a 100 year old provided that the loan to value ratio is low enough.

This is the key point not discussed in the article - what percentage of the price the buyer is financing. The difference between a long term loan with lower payments (aka one where the buyer is essentially trying to immediately finance an asset) and a bubble is whether the bank thinks that they can sell the collateral for more than the debt. Here it doesn't sound so good.