Yes basic income will reduce the incentive to work. Obvioulsy the higher it is, the higher the premium capitalists will need to pay to encourage people to work. At least the choice will not be work or famine.
There are a number of details with a basic income that are crucial apart from its level. The key one is the extent to which the welfare state remains free to all. If the basic income is reduced by an obligation to pay for healthcare then the “real” basic income is reduced below it headline level. If the basic provision of welfare and health services is “insufficient” or not nearly as good as if you pay for it, then the basic income is reduced. Expect plenty of discussion of this detail.
Is it affordable? Of course it is. As long as we keep.on spending:) if we don’t then the only way to.fund it is by taxing wealth…to a very great extent…and therefore building a very different and cooperation focused society.