I want one, but I'm broke in my late 20's. What's your secret?
A. Get into a high salary career (e.g. IT, law, medicine, engineering)
You may need to go back to school to get to where you want to go. Go to a state school to save on tuition, move if you have to to get in-state tuition. In IT you could sign up for a 12 week development bootcamp that has job placement at the end, but you'll have to invest about $12k to enroll. Over time though a career in software development will easily repay that investment many times over.
To jump up the salary ladder quickly in your career, obviously there's hard work, but a lot of it is advocating for yourself and setting yourself up to succeed. That means learning and demonstrating the skills that are worth more to employers, and switching jobs to get big pay jumps, or asking for (and proving you deserve) raises rather than waiting on the typical 3-8% annual salary increase. No one is going to manage your career but you, so make the moves that are in your best interest, don't wait for your company to take you to where you want to be.
B. Start a business, become successful
A riskier path but one with a lot of upside. You've got to be someone who is self-motivated, inquisitive, clever, stubborn, and very hard-working to succeed with your own business. If you're already in a high-salary career it's much easier to shift into working for yourself, setting up a side gig, or buying a franchise. This is way easier to do before you have kids obviously. I'd say that even if you can set up a side gig bringing an 10-20% of your salary per year, you can invest that money and start really moving up.
C. Real Estate/Investments
Others covered this but one way to build wealth is to buy real estate in areas that are developing, preferably something that needs some work. The vast majority of people don't want to take on fixxer uppers and that's where you can get big returns on investment. If you could get into rental property, even if it means renting out a room in the house you're living in, that can put you well on your way to building wealth. My wife for example, bought a foreclosed property in an area that was starting a wave of redevelopment. She got a 203k home construction loan and renovated the place nicely, now about 6 years later the house is worth more than twice was she paid. There was some pain and uncertainty involved but it was a calculated risk.
D. Marry Rich
Easier said than done, but at the very least, marry someone who's not going to be a financial drag. Also, get a pre-nup.