We caught up with The Agency founder and CEO Thursday at a construction site in South Los Angeles -- where the reality star and his daughters were helping build brand new houses alongside Habitat for Humanity.

Umansky says they're in the middle of one of their many build days -- a partnership with Habitat and Giveback Homes that sees members of The Agency dedicate their own time and money to offer affordable housing for folks in need. Now, there are eligibility qualifications.

In order to live in one of these houses, there's criteria -- like demonstrating a financial need; falling within the average median income between 50%-120%; having good credit; being willing to contribute sweat equity; being able to drop a small down payment, among others.

Anyway, MU made Thursday's work sesh a family affair ... with his daughters helping out at the building site with drills and staple guns in hand. Mauricio couldn't help but give them a hard time -- saying dad's not comin' to the rescue next time they need a lightbulb changed!

In fact, Umansky's daughter Alexia -- whom he shares with Kyle Richards -- even gave us a tour of the soon-to-be-finished house ... including the heartfelt messages she and her dad wrote on one of the kitchen walls

Ultimately, Mauricio noted how great it is to give back to the community ... almost certainly thinking of his own humble beginnings before The Agency took off. And just so you know, Mauricio and co. have built these types of homes for a wide variety of people ... everything from firefighters and teachers to vets and families with disabilities, etc. It's a good cause.

BTW ... Mauricio didn't mention Kyle during our talk Thursday -- instead choosing to focus on the great work The Agency's doing.