1) It will be much harder to find individuals willing to do certain categories of high risk or menial labor. You would end up having to pay a LOT more.
A much-heard argument this is, and I really wonder how much of it is true.
If you continue to pay the current wages, the basic income is the wage increase. The basic income is supposed to cover the basics: basic housing, basic food, basic clothing. Nothing fancy, just the basics to live a simple life. Now everything above this basic income goes to luxuries. Better housing, better food, better clothing, vacations, nice electronic gadgets. Of course this is simplified, I know, but it is the idea behind basic income.
These jobs (especially the high-risk ones pay a lot more than minimum already) will allow people to afford luxuries. Any job will allow them to afford luxuries. The interesting thing is going to be how wages are going to develop. Will they have to go up a lot, to entice people to take up the job? Can they go down to have the overall income level (basic income + new wage) stay the same as it is now (current wage)? Down part of the basic income amount?
For sure there will be people to take up any job - as long as the money is right.
The basic income changes this game, and I think it's really hard to predict in which way. After all, also other jobs will change wages. More desirable jobs may see their wages cut by as much as the basic income amount, automatically making other jobs more attractive even if those wages remain the same as they are now.
The desire "to take a job, any job" may be less - however you must remember that currently people out of a job also get a state income, a social security or whatever it's called. Much more cumbersome, but nevertheless also a form of basic income. Yet still people take up the menial jobs. Sitting at home watching TV on basic income may be fun for a while, but most people will get bored out of their minds. Some will look for a job, others (like me) will look for other things to do, other business ventures to start.