Boise leads the way for the nation's top build-to-rent markets, new research from CrowdStreet reveals. 

Investors are increasingly bullish on BTR communities, which are benefiting from a vast influx of tenants migrating away from pricey coastal and urban centers in favor of more affordable secondary markets. Millennials are key drivers of this trend, and they're willing to move to the suburbs for a little more space. But unlike generations past, they're also fans of amenities of modern urban cities—think dog parks, fitness centers, and common areas.

Cities like Boise and Raleigh-Durham have benefited from the population boom, have room to expand, and have the job growth rates necessary to justify multiple BTR projects, according to Crowd Street. Typically, the product type requires three to four times as much space as a standard garden-style multifamily property. And rental underwriting works, experts agree, in markets where land is inexpensive. In higher-priced cities, it's harder to find land that works well for SFR.