That is bullshit. At $20k a in Warsaw (75k PLN/year, 6250/month), your take home is about 5000. The absolutely cheapest houses, run down shitholes from the communist era with few windows and lots of stairs, cost at least 600k in the city limits. That's your entire salary for 10 years just to cover the capital. With a 30 year mortgage you'd be paying half your salary.
It's been a long time since I've made less than $20k and I do well, but I have a 25 year mortgage on a flat, much less a house.