They often have great jobs paying a very nice salary and are willing to buy a starter home (usually a condo). What they usually lack is a down payment so often get help from parents or friends.
Sometimes I will help two or three millennials to buy a home together where they live like roommates but get to deduct their proportionate share of the mortgage interest and property tax from their federal and state income taxes. Eventually, one of the co-owners wants to leave so the remaining occupants buy them out for their share of the downpayment they contributed and any equity that may have accumulated.
The co-owner who moves out may then buy another place or otherwise invest their equity. Buying a home in California is not easy for millennials but somehow they manage.