You buy the house with a mortgage, tying up your downpayment and obligating you to make monthly payments on the mortgage (which in the initial period go mostly to covering interest)
Before moving in, you realize that you could keep living at mom's house and rent the house you bought out at market rates. Let's say the market rate for your house is $5K a month, money that you can put toward your mortgage or building back up your savings/nest egg. (if you are renting your house out, some other benefits accrue to you, depreciating it, etc, but we'll ignore those, keeping that in mind in case you start thinking it also has some costs associated with it)
Now you have the thought... hey, wait a minute, does this mean that if you move into your own house, that act will cut off the $5K per month rental income, which makes it the equivalent of you having to pay the $5K rent yourself? Cuz, you could keep the rental income flowing if you rented another property, but if that one costs $5K too, the cash flow nets out to zero.
Could this be true? owning your own house doesn't save you on rent? Because investing in a house entitles you to the rent from the house, so consuming the housing yourself costs you the monthly rent whether or not you are the owner?
Yes, that's what it means. Buying a house does not save you money on rent, does not save you money on "housing consumption".
We need to give our kids a better financial education, there are so many myths that keep people on hamster wheels they don't know that they are on. This is the reason that housing seems "unaffordable"; why should it be any more affordable than rent?