I don't neither know the offer nor the qualification of your son. So i can only guess.
I guess the offer is a fulltime-job by a Sponsor and 800,- € for playing hockey or a halftime-job by a sponsor + half a day as a coach in the junior development + 800,- €. This is a regular deal for foreign players on this level. You can't get rich or earn a lot of money on the level 5. This is why you can find normally older player from eastern europe, the most of Czech, in this league as contingent player. In example the most german players playing for free on this level.
A fulltime-job in germany is regular 8h + 0,5 h lunch per day for 5 days a week. Often longer on monday till thursday and shorter on friday. The working hours are different. In regular we start earlier in Germany (for example 7 a.m. - 16 p.m. or 8 a.m.-17 p.m.).