Let’s say you start out making $70,000 a year. After deductions you’ve got about $50,000 to live on. Rent is going to cost you $1,500 per month and other necessities $1,500 (seems reasonable). So that leaves you $1,200 a month to save on a pretty tight budget. So In just seven years of living on the cheap and working you can get that 20% down assuming nothing goes wrong and you need no major purchases and don’t pay tithing or have kids.
Meanwhile, home values are appreciating at least that much (much more currently) which means all your sacrifices leave you pretty much where you were years and you’ve gained nothing.