Effectively UBI but declines as the person makes money.
Some rough calculations:
In 2019 there were 34m people in poverty[1], lets assume 2 people per household (lower than nationwide average of ~3) so 17m households.
Topping each of them up to above the poverty line (~13k/y/person) would be 26k / household / year would be 442bn (and that's assuming all people below poverty line make 0 dollars).
Not bad considering the government already spends over twice that (1tr) on welfare each year[3].
Like others have said healthcare, housing issues etc would still be very damaging to some, but it's an interesting concept that could put every person in the country above the poverty line for not that much $$.
I also like that it (theoretically) still encourages working since a) poverty line is still a lower quality of life. and b) when you're below the line and make more money, the government gives you less $$ but less than you are making. i.e. if you make an extra 2 dollars, the government stopped reduces by 1, or something akin to that.
[1] https://en.wikipedia.org/wiki/Negative_income_tax
[2] https://www.census.gov/library/publications/2020/demo/p60-27...
[3] https://www.budget.senate.gov/imo/media/doc/CRS%20Report%20-...