It's definitely not typical, but it's out there. Most cohousing situations are multi-generational, erring on the older side due to cohousing's beginnings in the 70s. You can check the cohousing directory to see if any are near you (there's one very close to me in Boulder, CO). I actually saw a condo for sale in what looks like one of the better cohousing buildings in the U.S. Durham Central Park Cohousing. I put some links below that may be helpful, including a directory of senior cohousing.

https://www.durhamcoho.com/

https://www.cohousing.org/directory/wpbdp_category/comm/

https://www.cohousing.org/directory/?dosrch=1&q=&wpbdp_view=search&listingfields%5B1%5D=&listingfields%5B46%5D=588&listingfields%5B34%5D=&listingfields%5B55%5D=&listingfields%5B63%5D=-1&listingfields%5B64%5D=-1&listingfields%5B12%5D=Senior&listingfields%5B13%5D=-1&listingfields%5B15%5D=-1&listingfields%5B16%5D=-1&listingfields%5B67%5D=-1&listingfields%5B20%5D=&listingfields%5B68%5D=-1&listingfields%5B69%5D=&listingfields%5B30%5D=0&listingfields%5B70%5D=