Did they do the early retirement thing? Like pay off their house ASAP while dumping their salary into 401k and Roth? I ask because my family member tries some

Did they do the early retirement thing? Like pay off their house ASAP while dumping their salary into 401k and Roth? I ask because my family member tries something similar, but it only really works because I pay for their housing. It just doesn't seem possible to live on $350/mo otherwise.