I think the problem would be with relatively inelastic things like housing. A landlord could easily just set their rates to 70% of minimum income and as other properties would be out of reach to those on minimum income there would be little competition. At that point you would get strong pressure to increase the minimum income or implement price controls.

We have had similar problems in the UK with private landlords renting out very poor quality housing at high prices to those on welfare. In the past we solving this by building lots of social housing.

I think a more sustainable way, if you want to implement a basic income, would be to have a low flat tax (say 10%) on all types of income, than divide the tax revenue across all citizens. That way everybody will cheer on the capitalists.

You have to account for price collusion, which is very difficult to prevent. Not to mention that all markets are not equally elastic.