I'm not too familiar with the expenses and such to run a company in Kristiansand, but the most businesses are located within and in the vicinity of the city centre, Kvadraturen.
There is also a pretty big industrial area 15-20 minutes drive east of Kristansand in Sørlandsparken.
As for rent I only did a quick search on the net and it seems like the prices varies from 12 000NOK (about $2300 USD) and upwards per month.
Hope that answers some of your questions. As for private accommodation I can suggest you go to www.agenius.no
Follow the menu to Career -> Living there's a pretty good explanation for basic living costs and such. It hasn't been updated in a while though, so the prices has increased some.
thank you very much for your kind hearted... it is do great help.