I think the historical average for San Diego is somewhere around 150-160
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In the last cycle, Clairemont bottomed at a ratio of about 150x in 1995-1996, so I doubt any long-term average gets that low.
(150K house, 1000 monthly rent)
As for the ability to cash flow with reasonable down payments (e.g. 25%) at a specific level of this ratio, it depends directly on interest rates (as SDEngineer pointed out above). So there is no set number that makes sense in all interest rate environments.
Believing that there is or should be a fundamental number for this metric would be to ignore one of the largest expenses (at least in the initial years) in real estate investment (The mortgage payment).
At the 8 % rates we saw in the mid 1990s one couldn’t really cash flow with the ratio at 150x.
With rates at 5% or so you COULD have positive cash flow with 20-25% down and a ratio of 150x.
