FARs concerning operations in foreign country

Hi!

I`m considering to buy a Columbia 400 for private and business
purposes. The aircraft will be N-registered, although operated in
Germany (which is legally possibly using a trust i.e.).
As I`m planning to earn my Commercial certificate, I was wondering
whether there were any FARs which prevent me from offering commercial
flights over here in Germany.

For the moment omitting possible restrictions possibly imposed by the
German administration, what are the regulations to such an activity?

Is the commercial transport of passengers in a single engine aircraft
allowed? VFR and IFR or only VFR?
How would I be supervised by the FAA? Can you point me to the relevant
FARs?

Thanks in advance for your replies...

Christian