Would someone be able to enlighten me on what the cons of a hypothetical situation in which everyone on the planet decides to temporarily get rid of the concept of money or currency, and pool our collective resources and ideas without worrying about who owes who?
This is called "communism". Go read Karl Marx.
If Xyrik is looking to understand the cons of such a system, Marx might not be the best place to look for them.
How much money would it take to engineer biological immortality for at least half of the world's population, within 20 years, with 99% confidence?