Zahavasdad – Someone once asked R’Matishyohu Salomon shlita the same mathematical question that you just raised.
I don’t remember the details exactly, but it was definitely to the gist of that the same way previous people have managed, is how future doros will manage as well. As in – it is sometimes unexplainable how people have managaged, but they have and will continue to do so (with Hashem’s help – No one has thought of bringing Him into the equation in this thread.)
It seems like the posters here don’t know many happy kollel families. I happen to be acquainted with plenty of them, and yes plenty people are doing it without parental support.
There are also plenty people who have a side income whilst in Kollel so I’m not sure why everyone here is painting such a black picture for an ideal life.
If one is not able to do this, there is the middle way of appreciating those who do it, rather than trying to make it sound wrong to do the ratzon Hashem (yes you can’t refute that Hashem is happy when people learn).