I used to live in CA and truly envy that your community colleges are so cheap. For my kids CC is $7k a year in-state, and that’s just for tuition!
The truth is getting scholarships for room and board is very difficult, and for most schools even if you get merit aid that will be your biggest expense. With housing being so expensive in most cities living off-campus isn’t always a cheaper option. If I were you I’d take advantage of 2 years of CC and then transfer. Since Cal Poly SLO is local for you that would be a great option.
And as far as how other people do it…fact is many have parents who pay or they have tons of debt. Few people will talk about it.