But some people in the room took his words as a cautionary note about Medicare-for-all and the ambitious Green New Deal, two liberal ideas popularized by a few of the more famous House freshmen, including Rep. Alexandria Ocasio-Cortez, D-N.Y.
While the more liberal freshmen have garnered much of the attention in Washington, many first-year Democrats hail from swing- or even red-districts and have struggled with how to respond to the emboldened far-left.
"He said we [as Democrats] shouldn't be afraid of big, bold ideas - but also need to think in the nitty-gritty about how those big, bold ideas will work and how you pay for them," said one person summarizing the former president's remarks.
Obama's words - rare advice from a beloved leader who has shunned the spotlight since leaving office - come as the Democratic Party grapples with questions of how far left to lean in the run-up to 2020. Most Democratic candidates seeking the presidential nomination have embraced a single-payer health-care system and the Green New Deal, an ambitious plan to make the U.S. economy energy efficient in a decade.
But some moderate Democrats worry a lurch left will upend their chances at ousting President Donald Trump. Notably, Speaker Nancy Pelosi, D-Calf., who helped organize Obama's meeting with the freshmen, has not put those ideas on the floor for a House vote - nor does she plan to, senior Democrats close to her say.
People in the room, who asked for anonymity to describe the evening, said Obama's cost warnings weren't deficit-scolding, per se. Rather he argued that voters care about the costs associated with policies and that Democrats should be ready to answer questions about how they will pay for idea while making big promises to constituents.
Obama gave the example of taxes: Even a liberal, he argued, could be repelled from supporting a liberal policy if it's accompanied by a major tax cut to their own bottom line.