An even more extreme example, if you want to start a business. If you have to save for 30 years to get your starting capital, you might already be too old to start.
For example this article https://archive.curbed.com/2018/4/10/17219786/buying-a-house... states that:
> the average teacher’s salary in 1959 in the Pacific region was more than $5,200 annually (just shy of the national average of $5,306). At that time, the average home in California cost $12,788
A house back then only cost 2.5x a teacher's salary.
According to Google, the average teacher's salary in California today is $83K (and this seems extremely optimistic, some other sources claim it's $65K max), the average cost of a house in California is $440K.
That is 5.3x in the best possible case. Meaning that people today have to work more than twice as long to be able to earn the amount of money it takes to pay for a home... And that's not even counting the interest they need to pay on top which roughly doubles that amount yet again!
This asset inflation was caused by banks. By allowing people who could otherwise not afford to buy a house to buy one (thanks to loans), they artificially increased the demand for housing (which is somewhat limited in supply in urban centers where work is available); and in accordance with the law of supply and demand, this drove up the price of properties.
Loans allowed reckless people to participate as buyers in the marketplace and this punished savers and cautious individuals. Many of these reckless people, eyeballs-deep in debt which they couldn't afford, then turned to criminal or unethical activity to make money. Studies have shown that financial stress leads to increased levels of criminal activity. Debt causes financial stress.
Banks harm not only the people who are taking loans but also the people who are not taking loans because it turns assets which savers could have easily have been able to afford within a few years into assets which they can never afford by saving their salaries.
Even without money, a house would cost something - you would have to get the building materials, the ground to build on, and the time and work to build it. This has nothing to do with banks. The banks just help you to pay the cost upfront.
There are other ways to do it, like the Amish coming together and building a house in a day. They still use a lot of work hours, distributed over many people. And it only works out if you are also Amish and "pay it forward": for now, you give other Amish "credit" by helping build their houses. When your turn comes to move into a house, you'll get that credit back because they help you build your house. That sounds great, but it doesn't provide the freedom banks do. If for some reason you don't want a house in an Amish community, you won't get your credit back. Islamic solutions have similar issues (credit is illegal, so they either borrow from non-muslims, or they also have a "pay it forward system" where every member of the community chips in when somebody wants to marry and build a home).
In many developed countries like Australia, there are many people who own 10+ houses which they bought using debt and rent out. These people are monopolizing ownership of real estate and forcing people who don't have preferential access to credit to rent from them instead of buying.
The injustice of the scheme comes from the fact that not everyone has equal access to credit from banks. It's an unjust qualitative social process which some people are locked out of.