So what makes housing affordable? A simple guide is that a family shouldn’t spend more than about 30 percent of its income on rent and utilities. (Although you can argue, I supposed, whether the number should be higher or lower.)

For one thing, that makes basic common sense. For another, using the 30 percent metric means the other 70 percent is out of the picture — it doesn’t matter what else they spend it on.

Anyway.

Every year, the National Low Income Housing Coalition (NLIHC) compiles a report that figures how much a household has to earn to afford basic housing in various regions of the country — “basic” meaning “a modest two-bedroom apartment.”

They call that figure the “housing wage.”

Example: If such an apartment typically rented for $600 a month (including utilities), based on the 30 percent rule the family would have to bring home about $2,000 a month.

There are about 176 working hours in a month, so that family’s housing wage would be about $11.36 per hour.

Pretty straightforward.

Except that in real life, the average housing wage in the U.S. is $18.25/hour. The average renter earns $14.15. Ergo, you need at least two people working to afford it. (Which makes sense, as we’re talking about a two-bedroom place.)

Of course, the Federal minimum wage is only $7.25, so you’d need three people earning that to afford it. So if you earn minimum wage, better find a couple of roommates and prepare to be cozy.

In Washington, D.C., the housing wage is $28.96/hour. And just to toss this out there, on any given night (according to HUD), about 650,000 Americans are homeless.