If one is a good saver and you’re good with the stock market and starts with $100,000 and hold stocks for 30 years you’ll accumulate around $1.6MM-$3.5MM without doing anything 

If one is good as an employee and you work for 30 years at a good company and you’re good with the 401K plan and maybe trade here and there you can accumulate around $3MM-$4MM when you hit retirement. 

If one person has around 10 rental properties with a loan and you hold them for about 30 years the equity plus the rental income you’ll accumulate around $7MM-$10MM

If you’re a good real estate developer and build around 7 properties per year and make around $150K per property that you build and sell and you own the majority of the equity you’ll make around $20MM-$25MM in 30 years.