The argument "where does the extra money comes from?" is looking at it the wrong way. The right question is: does it stimulate the economy?

Currently, people do not spend, and accumulate as much as they can, because they are being told there is a crisis (not for the richest). In Western Europe, governments generally agree to make "reforms" destroying all social advantages inherited from the reconstruction after WWII. In France in particular, the biggest investor if the "local communities" (cities, departments, regions), but the national governement now lowers the money affected to them, leading to less investment from these public investors, killing a lot of jobs.

So we don't care where money would come from. What we need is somethin that gives people confidence in their future, like a stable job. If you have a job but feel threatned in it every day because your boss can replace you with the "reserve army of labour", you tend to let your social advantages go away, and earn less. Collectively, this profits to the richest who drain huge parts of the economy to use it in bubble speculations - which also profits them even when the bubble explodes.

Besides, we had to transit in a few decades from a social model where women did not work to a model where women now are an active force. Couple that with huge productivity improvements... and we don't need a full time job for everyone, for everyone to live correctly.

So where does the money come from ? Last of the question to ask. First question : what do we want to do with our society, what do we want to do collectively to stop having the poor constantly fighting each other ?