People will get food and shelter for free only if they work free for 40 hours (in USA). So this will be the motivation for them to work. No work means no food and shelter. In USA all full time employees work for 40 hours a week. This number can change in future depending on how the MLE evolves.
The work is defined as any meaningful effort desired or required for the benefit of the society. Entertainments and sports will also be considered as work. Although many work types will vanish or become meaningless in MLE, but all facilities that will manufacture goods or provide services will be considered as meaningful work as long as the society needs them.
Many work, like research on the migration of monarch butterfly, which appears meaningless but funded now, will be considered as meaningful under MLE.
In MLE people will have tremendous surge of energy for work. Because they can now work on their own ideas, and on the jobs they really like. They can go to any factory anywhere in the world and start working there. The factory owner will not have any problems in hiring them, because the labor is free.
In fact unemployment is the greatest punishment in life. Nobody likes to sit idle. Everybody wants to contribute to the society. The MLE will give people the opportunity of their heart’s desire.