"Essentially what we're seeing in a lot of these cities with rapid growth like Austin or Denver or San Francisco is the rent prices are going up so much it's actually doing wonders for the other [nearby] cities," says Sam Radbil of ABODO, which tracks rent prices. "The same is happening with Minneapolis and St. Paul. People who, say, couldn't afford living in Minneapolis are venturing out a little further and it's affecting rents in St. Paul."

According to ABODO's National Apartment Report, the average rent for a one-bedroom in St. Paul rose by 11 percent over the past month. What was $1,070 in February pushes $1,200 in March. That increase is big enough for the fourth highest rise in cities across the country, trailing only Pittsburgh and Indianapolis at 12 percent and Portland at 14 percent.

Meanwhile, one-bedrooms in Minneapolis went up by 7 percent during the same period.

A collusion of forces continues to power the Twin Cities' bullish rental market, says Radbil. Millennials flock here for good jobs. Baby boomers downsize from suburban homes. A stable of colleges and universities supply a steady market of renters. It all meshes to make these the good ol' days for landlords.

According to ABODO, one-bedroom units in Minneapolis two years ago rented on average for $900. By March 2016, that figure climbed to a rate of $1,174.

Inflation in St. Paul has been even more abrupt. In March 2014, one-bedrooms averaged $780 per month. This month, a one-bedroom pad comes with an average price of almost $1,200.