Do I think anyone has a fool proof way to do that?

I agree that the 1% rule isn't foolproof (it may even be fool-friendly) and to Marcus' point looking at Capex and YoY rent increase and other factors is probably more important (not to mention the type of neighborhood, like, there could be a great "on paper" deal but if you look at the area and people are stealing AC units it might not be so good on your $paper$). 

I can't afford to have deadbeat tenants, although it's not foolproof, I can't invest in an area that doesn't have laws to protect a landlord. 

As part of my due diligence, I always ask for proof that the prospective tenant has paid the last month's rent.I personally don't care how much praise the current landlord gives me about the prospective tenants, that could be a smoke screen to get rid of the trouble makers as fast as he can.While it's not 100% fool proof, if I don't see a cashed check or other proof that the tenant has paid his current rent, I'm going to put this tenant through the grinder to get every single detail I can.I consider this kind of check to be more important than an Eviction check.

It's not totally foolproof, but he feels it has helped weed out some bad renters.

There's no foolproof way to tell, but if you've got a long enough lens and the area is doing well financially, you should be fine.The key to this gentrification was the development of San Francisco--as all those tech jobs moved to SF, housing prices really started going crazy and pushing the artists out.

but that conclusion isn't foolproof, because we do have some very affluent areas that are down 11%, and there are also some very low SES areas that are up 5-10%....so, I don't know...

What about Bitcoin, While block chain is a great idea, it is not fool proof.  

Simply judging a list price or assuming the value based on the current rent is not a fool-proof method of evaluation.

Though I wouldn't want to say any method is foolproof becuase probably nothing is.