> I really don't understand how a 'basic' income is supposed to work.
Its like the Alaska Permanent Fund[1], but with a broader -- and by design growing with the economy -- revenue base.
> What if I spend my basic income on drugs and hookers? are you willing to let me starve? what about my kids? If not, then the basic income can't actually replace the existing social programs.
Sure, it can still replace existing social benefit programs. For your kids, well, we already have provisions for taking children from the care of parents that abuse or fail to provide for them, and putting them in the care of the State with the parent responsible for support costs; allowing either redirecting the children's basic income from the parent to the new support provider (in a system where children have basic income) or diverting some defined portion the parent's basic income (in a system where children do not get allotted their own BI) to pay support costs is quite natural; this doesn't create an additional social benefit program.
As for you, some BI supporters would let you starve. Others might support having transitional food/shelter programs (which would be an additional short-term benefit program) available to avoid people falling through the cracks, but make the beneficiary responsible for the cost (possibly diverting some share of future BI payments until that debt was paid).
> If nobody need to work, then if employers want employees, they have to pay more to get them, which makes prices rise, which makes your 'basic' income insufficient again.
Under realistic assumptions about elasticity, Basic Income would have some effect on accelerating price inflation of goods demanded at the low end of the income distribution, which would mean that the quality of life any level of UBI could sustain with no outside income would be somewhat less than one would expect with the same amount of income before the UBI became available. But overall, those receiving the UBI would be able to afford more than without it.
Further, UBI can cut employer costs (while it reduces economic duress to work, it also reduces the need for a minimum wage and many UBI proposals have it replace the minimum wage; it also means bad-fit employees will have less resistance to moving on, and that people will generally have more freedom to seek optimum job fits -- which are good for workers, but also most productive for employers.)
And most people don't just work enough to meet basic necessities if they are capable of getting more, so most people able to do economically useful work probably would even with a UBI that met basic needs -- people like luxuries.
[1] https://en.wikipedia.org/wiki/Alaska_Permanent_Fund