Not necessarily. It's straightforward to make it revenue neutral.
You make it revenue neutral for the average tacpayer. If you want UBI to be $1000/month, you increase the average tax by $1000. The average taxpayer still benefit because even though they don't get more money, they have a safety net.
People making less than average get more UBI than the tax increase, and those making more pay more.
Most people get more money because the median income us a lot lower than the average.
This assumes all goods are wanted and consumed equally. Housing, milk, meat, eggs, etc. do not see downward pressure from this.
Is it straightforward to get Congress to make it revenue neutral? And to keep it revenue neutral? I don't think so. Politicians find "free money for everybody" to be too easy a way of getting votes.
Right, but people with lower incomes spend, and mostly on necessities, I think the idea is that most of those necessities would become more expensive (naturally or artificially due to price-fixing) if the poorest suddenly had more financial power. In the system as it stands, it seems to me like it'd just result in a bunch of money going to grocery giants and their suppliers, landlords, medical, etc.