That resentment is natural given that the people they're renting from often had their foot on the property ladder in their twenties. For millenials and younger that's the exception unless you've had help from your parents.
When I moved from home (almost 20 years ago) to study, I had to chose between living on campus - which came out to around $150 / month in only the rent, rent private for $200-$350, or purchase a smaller apartment. The apartment would cost around $50k-$100k, but back then the banks would give you a loan with as little as 5% down payment on the mortgage. A 20 year mortgage would cost around $200-$400 a month, depending on price of the apartment.
Coming up with $2500-$5000 for a down payment was not that difficult, even for someone just finished in high-school. One could easily save that up over a summer or two.
Fast forward 15 years, and the same apartments now goes for $250k-$350k. Rent is $1k minimum, and all the rooms on campus are either full and waitlisted, and you can only live there for 2 years anyway. Oh, and banks require a minimum of 15% for the down payment. And that's for the smallest, most basic "starter" units. The 2008-2009 crash killed all momentum, and building only reached the same pre-crash levels some 5-6 years later. This vacuum led to used housing exploding in price.
I think the resentment comes from the fact that many young people are paying $1500 in monthly rent, while a mortgage for the same unit would come at $1000 / month. They go to the bank and apply for a loan, but the bank says "Sorry, you need to save up more for the down payment". Next year the same house is 5% more expensive, while the rent has also increased in the same manner - but salaries have not.
Probably not a problem for us that are working in high-paying fields, but for regular people - especially young ones starting at the bottom - it probably seems like a race where the goalpost is being moved further and further away.
