If you abolished every single government program and fire every single government employee, right from the DoD down to your local playground, from congress to the schools, never mind every single existing welfare program, assuming that tax revenue somehow managed to stay at the same level, what with no IRS to collect it and 22 million newly unemployed public sector workers, you could barely afford to pay a UBI at the minimum wage, never mind attending to the people who might legitimately need more help (also, no roads or schools).
UBI is either going to require cuts of a depth never proposed, much less enacted, in any western country, ever -- or be too small (perhaps a hundred dollars a month) to live up to its promises.
Every time you want to raise enough revenue to give the 99% another $1,200 ($100/month), you need to raise taxes on each single member of the 1% by $120,000. And that's on average incomes of a million.
I think almost everyone would want to work on $13-$15k a year. However, they'd work part time.
And tbh, for our current welfare system, that is essentially what happens already. They work minimum wage jobs, part time, on call.
It's kind of silly to discuss the details when there aren't any. People need to be open to giving cash to the poor to even begin thinking about how best to implement it, and the US at least has been going in the opposite direction since the original Clinton welfare reform, which emphasizes employment assistance over direct monetary assistance, with mixed results.
Personally, I think it's throwing money away without also addressing healthcare costs, including nutritional reform. Sugar is only cheap when you ignore the costs of obesity we all bear in increased premiums. This is the only way of which I can conceive to implement some form of cash relief without cutting into benefits.
* focusing on the wealth/profit generated by a surge in entrepreneurship from the millions suddenly motivated to start successful businesses
* focusing on the unlimited wealth created by robots/asteroids/solar in space which will fund any program we wish
* focusing on how we can't afford not to try BI, i.e., the default system is a financial failure anyway so comparison is pointless
* taking the position that BI is only replacing current welfare programs (until it's pointed out that current programs would not support anyone if spread around)
Occasionally, someone will admit that they are proposing a 100% tax rate, which is about what such a system requires. Even more occasionally, it's admitted that every country must implement a 100% tax rate at once to avoid mass emigration of anyone earning more than ~$20k/year.