I think around 2001 things started bubbling. For example, this place near me:
11515 Caminito La Bar APT 81 San Diego CA 92126
Sold for $118k in 1999. That’s a 2br/2ba condo in a neighborhood where rent was $1200+ (it was $1100 when I rented in that hood before buying). If you bought it with 20% down, 30 year loan, 6% you’re looking at $652 including tax, add in $180 for the HOA and that’s $832 to own vs. $1200 to rent.
In 2004 that unit sold for $370k. Tripled in “value” in 5 years.
It’s amazing that in today’s mindset nobody can fathom a mortgage payment being less than rent.