I've heard that it's difficult for co-ops to borrow money, something about there being too many owners.

It seems to be a pretty rare structure. In Canada we had Mountain Equipment Co-op which was a great national company for a bit until the leadership was captured and they sold the entire thing off to a corporate interest. It's lost all ethos and is just a very expensive lifestyle brand now.

There's a gal on TikTok, I think her name is Madeline, that runs a business that she owns as sole proprietor (to please banks) but everyone in the company including her makes exactly the same day-rate pay. Decisions are made democratically. She's writing a book about her experience doing this.

All structures are vulnerable to capitalists though. As soon as people get complacent someone smells profit and exploits it.