Canada

As UBI is not a lot per person and only goes to very low income people

It goes to everyone. But as it also goes to wealthy people, you can tax them more in that way, and so basically there's no real extra expense there.

Especially with that single-payer healthcare we have. The unit rates for things like Dr. hours or beds in hospitals are enormous. If we can cut down on the number of visits required because people have somewhere safe to live and aren't getting injured/sick living on the street, we could save huge amounts of money. Add onto that the cost of policing and/or incarcerating them, plus the economic benefit of having downtown areas feel safer for people, thus encouraging more people to live/work/spend time in those areas.