It’s bad for everyone if an MA starts their apprenticeship, then leaves shortly after because the training isn’t suitable for them or they’re not committed to the role. That’s one reason why all MAs must have an initial assessment, normally within their first two weeks of starting.
If you’re concerned, you can arrange for an extended assessment period with the employer during the months before they start the MA. This gives you, the employer and the trainee time to decide if this apprenticeship is the right choice. During this extended period the employer must pay the potential MA at least the National Minimum Wage as they’re not eligible for the apprenticeship rate at this stage.