Take 100% of the wealth of everyone with more than $1B in the US and you get $23k per person / $33k per adult. That's a good amount of money; the adult number would be enough to live off of in the right parts of the country. It's about 4x the annual welfare spend. But then next year comes, you have to find the money again, and you're out of billionaires.
Change billionaires to top 1% wealth holders (>$13.7M) and things are more tenable. You could run the $33k/adult-year program for 6 years, or invest at 7% return for $13k/adult-year. You probably can't get a 7% return for at least a few years after second-order effects on the economy and I don't know what those effects would be long-term, but these numbers at least pass the smell test.
An important point is that this wealth is purely notional. It doesn't exist as cash you can distribute unless there is a liquid market, and confiscating it would annihilate any liquid markets. Furthermore, ~70% of that wealth in the US is non-liquid generally.
That wealth doesn't become cash unless there is a giant pile of cash owned by someone that can be used to buy the assets at the notional value. Where is that cash going to come from? It can't come from the government printing money since that is just inflation with more steps.
Change billionaires to top 1% wealth holders (>$13.7M) and things are more tenable. You could run the $33k/adult-year program for 6 years, or invest at 7% return for $13k/adult-year. You probably can't get a 7% return for at least a few years after second-order effects on the economy and I don't know what those effects would be long-term, but these numbers at least pass the smell test.