That is the reality of an apprentice cadet programme.
I do not know if your figures are accurate, but on the assumption that they are, they will be Gross figures and not "take home". To give you a general idea of what 24,000 euros (£21,500) looks like from a monthly take home standpoint:
£1,791.67
Tax free Allowances £622.92
Total taxable £1,168.75
Tax due £233.75 £53.94
50% tax rate £0.00
40% tax rate £0.00
20% tax rate £233.75
National Insurance £142.72
Total Deductions £376.47
Net Wage £1,415.20
That £21,500 has been whittled down to around £16,982 per year.
Depending on your financing, that isn't far off what the repayments would be for borrowing your training costs. In effect you would be living off your allowances. Those are only paid when you actually fly. They are taxed, not paid when you are sick, off, on standby, on leave, or during many forms of training.
Whatever the terms of this scheme, they usually remain in effect untill you have amassed a certain number of hours in company service. Generally speaking (if you fly a lot) this is around 2 years. You then move on to the regular salary structure.
Bear in mind that this is "apprentice level" remuneration. It is attractive to the company, and that is why you would be taken on from an approved course with so little experience into the righthand seat of a commercial transport.
I am afraid that the reality is, you will need to look at a much longer amortization period for your training costs than 2 years. Other companies may offer more or less, but the methodology is more or less the same.