How big was their house? 3 of my 4 grandparents grew up in multi-generational houses, all of their parents were very working class, and yes they "afforded" raising kids and housing their elderly. Their houses were not bigger than 100 sqm though. All shared rooms, and there was typically 1 bathroom for the entire household. Clothes were hand me downs and meals were only what they could afford, so the meat in their diet was mostly weird low quality stuff. They shared bath water! The lifestyle described is 100% still attainable today. It is your parent's choice not to have grandparents in the house - in line with societal standards today, but certainly not impossible.