Some suburbs around New York City are becoming decidedly less suburban, as new apartment buildings and condominium communities close to mass transit help expand the downtowns of these villages and towns. Multifamily housing is also popping up near highways and main thoroughfares.

Young professionals seeking more space than they can afford in Manhattan or Brooklyn, empty nesters looking to downsize and leave the snow shoveling to others and, to a lesser extent, millennials moving out of their parents’ basements are leading the charge to a more urbanized suburbia.

The new developments are attracting people like Rima Chodha and Varun Thakral, who knew they would have to take baby steps when they made their move from the city to the suburbs. Leaving their one-bedroom apartment in the Hell’s Kitchen neighborhood of Manhattan was “an uneasy and frightening prospect,” said Ms. Chodha, 31, an advertising executive. And maintaining a single-family house seemed like too big a leap.

But the three-bedroom townhouse at Country Pointe Huntington in Huntington Station, N.Y., which Ms. Chodha and Mr. Thakral will move into in the spring, seemed like the right fit. The 76-unit community, with prices from $409,000 to $600,000, is within walking distance of a Long Island Rail Road station.