One way to think about it is the Spread between the cost of owning vs the cost of renting. For example, in SF, the spread is very small and hence favors the renter.

Here's an example: In SF, your cost of ownership is roughly 2% per year (1.4% property taxes, 0.5% for Earthquake Insurance, 0.3% for repairs and depreciation and HOA), which comes to a total of 2.2%.

The average Rent for an equivalent house is roughly 3% of the purchase price per year. So the spread is just 0.8%. Which means, if you can take the equity you would have put into the house and put it somewhere else, as long as you get a 0.8% real return (easier said than done with the high PEs we're facing), then you'll be ahead with renting. And of course, if you need to do a mortgage as most do, that adds a additional 1-3% to the cost of ownership making it even more in favor of the renter.

Now keep in mind, here in SF, it's pretty extreme. Most places have a much larger spread between renting and owning.