It's long talk broken into 7 parts on youtube. I highly suggest everyone watch this when they have an hour to spare.
TLDR: Free energy and UFO's are real. Research "Zero-Point Energy". Quote from Dr. Greer's website "For over 100 years, advances in electromagnetic systems have allowed for the creation of over-unity (more out-put than manmade input) power generation via the zero point energy (ZPE) field and quantum vacuum. Technological progress in the areas of advanced physics and electromagnetic systems, if appropriately supported, will enable humanity to live on the Earth with a minimal footprint with genuine long-term sustainability. For over 100 years, these advanced concepts in energy generation have either been ignored or actively suppressed due to the power of fossil fuel based economic and industrial interests."
https://siriusdisclosure.com/energy/
The reason we currently are not using free energy is because every time some genius comes up with a great invention for free energy or other disruptive technologies, a corporation would come by and offer that genius millions of dollars to essentially buy ownership of their free energy technology. The genius then says "Well, this corporation just offered me life changing amounts of money so I'm going to sell this technology and be rich for the rest of my life!". Then the corporation takes the technology and puts it on a shelf in a vault, never to be seen again.
OR
Government agents would show up at the inventors house and say "We are going to take all of the stuff you just made and there is absolutely nothing you can do about it."
Part 1: https://www.youtube.com/watch?v=VeXVsybEQPQ
Part 2: https://www.youtube.com/watch?v=4o4x6DJFXr0
Part 3: https://www.youtube.com/watch?v=cPNUyu7GMnY
Part 4: https://www.youtube.com/watch?v=vKyUQyRpJTQ
Part 5: https://www.youtube.com/watch?v=Q3zFPi1XzIY
Short version:
He was chief of emergency medicine at a hospital for years, a very lucrative career. Along with that, his wife also comes from wealth.
So like Trump, he did not 'need' to do this for money. Indeed over the years he has poured a lot of his own resources into disclosure work.
As with Trump, he left his wealthy hospital position to focus on serving humanity, after being approached by unnamed contacts reportedly concerned with the covert programs and lies.
And his various working groups were always a kind of mostly volunteer, shoestring-budget type operations. Like Q anons, doing it for love. And for which Dr. Greer has made many kinds sacrifices over the years, aside from money.
For instance he is well over 6 feet tall, but in using his group's funding - at times he would unpretentiously (and uncomfortably) pretzel himself into an airline seat and fly coach. Not to mention he has literally risked his life to do all he has.
The man is dedication itself.