The trickiest part for me is always healthcare costs. If those weren't a factor I could give a pretty good estimate (for places I've lived) of what I feel a 'living wage' was.
Iowa, one of the bigger towns (sure you could buy a dump an hour from anywhere for cheap, but that by definition can't work for the majority of people), you could probably find a place to rent in the $800 range for a decent place (aka not next to a meth lab). I feed my family for about $400 a month, but recognize I'm a bit on the cheap side there. Car insurance, utilities, internet, clothing costs, bit left over to do some actual living on, maybe a bit left to put away. I think overall you're looking at ~$2000 a month on the pretty low end. So that'd be in the range of $12 an hour (post-taxes) here in Iowa if there was some sort of universal healthcare.
Central Texas, more expensive, probably closer to ~$15, South Dakota a bit cheaper ~$10.