My sister lived in a Catholic Worker house while she was in college (she didn't work there, she just lived there) and my cousin and her husband worked and lived in a Worker house about 10 years ago.
Worker houses were started by Dorothy Day. You could probably find more info on-line by doing a search for Dorothy Day.
As far as I know, Catholic Worker Houses are accepted by the church at large. Most volunteers work at a house for a period of time (a year or two, often out of college or as young adults). Alot of people stay connected to a particular Catholic Worker House and it's particular mission.
The house that my cousin and her husband worked at was in the California Bay Area and specifically for immigrant/refugee teenage kids from central and south america. My cousin and her husband were legal guardians/ foster parents for these kids. Now my cousin and her husband own a house and regular jobs, but they are still very committed to living simply and working for social justice.
My cousin was also very involved in the Catholic Worker House in a low income neighborhood here in Chicago before she moved to California. The house here has a soup kitchen, food and clothing pantry, etc.
My husband and I are Catholic and are working on living more simply and working on issues of social justice. Dorothy Day was an amazing person, but not somebody that I want to model in my life as a healthy parent. I want to work for social justice and live simply (as much as I can as an American with a house, car and computer!), but I don't want ANYONE (including my child) to live of life of POVERTY...
If your friend is dating a guy who lives at a Catholic Worker House, he may not plan on doing that for his entire life. Or he may - and I agree that that is probably not the most stable environment for a child. But we have alot of friends who did volunteer stints for several years (Jesuit Volunteer Corp, Peace Corp, etc) who go on to do other work (social workers, ministers, nurses, etc) and they are GREAT parents.