Will people with non-great jobs around the basic income level keep going to work, or will they stay home and maintain their current living standard, or will they keep going to work, and roughly double it?
If many people choose to stay home, the cost of the services they provide will rise quite dramatically. This will have some hard to predict consequences across the economy. Some of the services will just be foregone with little tangible effect. Lawns will be mowed less often, street swept less often etc. Slightly worse impact on the economy will be when busy people decide to forego help, such as cleaners, babysitters, handymen etc. and do the job themselves, competing with either or both work and leisure time, which impacts either or both productivity and quality of life.
The most direct impact will be the rise in cost of services that can't be foregone or "taken in-house". Trash-collection, several bits of the retail supply chain etc. This will raise the cost of everything for everyone.
Also, besides these impacts, there's the human element. If a person makes the short-term decision to not work (and not studying or working on a startup or something similar), that person moves further and further away from ever participating in productive labour. I'm a bit old-fashioned on this, but I consider allowing people to go idle, long-term like that, is a grave failure of society. Many people who start in unpleasant low-wage jobs, don't end in them. Those who never start any job(/education/productive activity) at all have no chance of progressing beyond them.
But the worst is that taken together, the rise in prices will create a strong force towards getting rid of low income jobs, which will raise the bar significantly for those at the bottom, committing many of those willing to work to not work.
This is all speculation, and it's all dependent on the level to which low-income people will or won't chose to work.