My wife (Swiss) and I (GB) plan to start a business May'09 as an einzelfirma or Kollektivgesellschaft. Until then we plan to go travelling for the winter (approx 5 months) and to rent her house out. Is it possible to use the house renting as our business during the winter months so we can get all the necessary paperwork (my B permit, Kollektivgesellschaft etc) already in place, ready for next year?

Why would you want to do that?

To get a sensible answer you'll need to provide more info.

Is the business you plan to start next year anything to do with renting houses? Or do you think you can wangle the rental income (presumably from a house that you own) through the books of a business and pay less tax. But you can put all sorts of expenses against rental income anyway...

We will be going into the B&B business, and would like everything to be in place asap after our return. We plan to lease a vehicle at this time and the leasing companies want everything in order before they will look at us. We don't want to be held up by beurocracy for a couple of months...