As someone in my 30s, here's some advice for 20-year-olds:
Never take out any loans.
Never sign any contracts. Master GPT and let it help you in everything.
Other advice is meaningless; it depends on luck, background, and genetics—everyone is different.
Any loans include Alipay, online loans, credit cards, mortgages, etc. In short, never borrow money from anyone; always save money.