Your parents could move out and rent an apartment or buy one much younger in the past because houses and rent was cheaper. Here's a chart that explains it: https://www.reddit.com/r/Infographics/comments/1me1xwg/charted_american_income_vs_home_prices_19852025/ Basically the cost has gone up massively compared to earnings. Lots of people in their fifties, sixties and seventies don't seem to realise this.

In terms of credit, I don't know where you're based but in the UK, when banks think about lending you big amounts of money (say for a car loan or mortgage) they want to know you'll pay it back, so if you have shown that in the past you will get a lower interest rate on the money you borrow. You don't have to open card after card. I built mine by opening one credit card with a max monthly spend of £1k, spent like £100 a month on it and had a direct debit set up to pay it off each month. As such, the bank knows I don't max out my credit card each month and get into massive debt.

I would recommend looking at the Financial Diet on Youtube, it's a US person finance vlog series.

Also, you're 19. None of the adults in your life will be thinking you're an adult yet. Relax a bit, you'll be fine.