>>512670932 (OP)Partially correct. They don't necessarily need to make the new arrivals into debt slaves (but they'll happily do that).
Adding more people obviously lowers the "average debt per person" and adds more liquidity into the system, as even if the new arrivals are going to do something like get a mortgage they'll have to do things like show some employment history and make a downpayment.
Another reason is that it helps to hide the issues with the property market. If the population had remained stable or this natural decline (as the older larger generations died off) then people would naturally be asking why housing costs so much. They don't want the average joe public to realise that it's because of the devaluation of the currency.
The average normie retard still thinks they've "made money" with their house having gone up in value, but there is a point where it can get into Zimbabwe territory. Same thing even for basic goods and services. If you've absolutely flooded the place with immigrants you can hide behind the idea that there's just so much extra demand now.
If people actually use any sensible metric, they'll see that things they pride themselves on (for most normies that is the house) has actually gone down in value when you adjust for inflation and that the mass migration is trying to artificially prop it up. E.g. without plenty of "cashflow" for those fresh mortgages (whether that's the new arrival getting one or he's renting and paying off some boomers mortgage) keeps the banks solvent and adds liquidity into the system.
They know in a low of cases that jeets or nogs are net negatives. They need to "stimulate the economy" and keep money moving around. If you don't do that, you get "shocks" to prices. E.g. lack of liquidity causes prices to rise/fall sharply. Their main fear is that you get a "runaway effect" where sharp price increases lead to self-fullfilling prophecy (people overpay in anticipation of further increases) and hyperinflation.