Isn't it part of the point with basic income in that it doesn't disappear if you have a job?

The choices would be "basic income" vs "minimum wage + basic income".

There is also the fact that there is no inherent reason why toilet washers should have minimum wage. It's exactly because of economic uncertainty among the lower class that they can be coerced into accepting such sub-par situations such as doing an undesired job at low wage, when it's more logical that an undesired job should offer more pay than a desirable job.