Hi Mora,
Let's name this MBA student as 'xyz'.
1. 'xyz' is permitted to work 90 full-days or 180 half-days as student. (If xyz is a spouse of blue card holder or on valid family visa he /she can do job as well as studies but in consulation with ABH ! )
2. 'xyz'- Be positive !..well I don't know the cost of MBA here. However, can 'xyz' recover his actual financial costs by working in a small time scenario??. Food for thought!!

. Well NE....
a) With normal Aufenthalstitel (permit) -NE can be applied provided 'xyz' has secured a valid job contract and subsequently 60 months of contribution to RV.
b) However,with blue card (which has minimum requirements,skills,salary e.t.c to be fulfilled) NE may be applied after contributing to the RV for a minimum of 21 months , along with B1 lang .
3. The bank statement should be financially stable for the start up/registrtn and ofcourse consultation is required with ABH.
Regards,
P:S- not a legal advice