If (when) we go BC in December and move to Germany shortly after we won't have a clue about our living expenses until we have lived there for a little while

We know how much rent we will be paying, but that's about it. We don't know about anything else really. We have asked the question about cost of living etc. but at the moment it's all a bit hit and miss.
Would the OR want to impose an IPO straight away so as not to loose any money paid into the BC or would he/she be willing to wait until we know what our outgoings are going to be?
Any ideas anyone?