I can't find the numbers atm, but one of the think tanks did a break down of it, and it came out that you could eliminate homelessnes, malnutrition/hunger, and all fund all social services for everyone for 18 billion per year.
Then the cost is actually 18 billion times the number of years you want to fully fund these programs. I could see an argument that the longer you fund free education etc. that less and less people would need the programs but...
I just read an article on the difficulties that some countries with high social spending (and corresponding high tax rates) are beginning to run into problems keeping their programs funded.
Turns out that more and more people are deciding it is easier to just float than work for life's necessities.
Everything in moderation is the best solution IMO.
I'll dig around and see if I can find that article....