Quote from Ghost of Cutten:
The NINJA loans etc are a symptom not a cause of a bubble. If a property market becomes 100% overvalued, even people who put down 20%, 30%, 40%, 50% deposits lose all their home equity.
The mistake to avoid is being overexposed to real estate when prices reach historically extreme bubble valuations. Make sure you can survive a 50% or even 75% fall in prices without being financially devastated.
To look at valuations, just compare real estate prices to things like local incomes, rental cost for equivalent properties, and so on. Then look at the historic ratios for your area and see how out of whack they are. If it costs 2k monthly all-in to own a place, and only 800 to rent it, then prices are out of whack. If historic price to income was 3-4, and now it's 8-10, then it's a bubble. If rental yields used to be 5-7%, and now they are 2.5%, it's a bubble. Etc.