do you need license for starting webhosting company ?

You'll need a business license from the city/county you live in.

Where do you live? Usually you can get one at the county court house where you live.

You'll also need a DBA (doing business as) - most states require you having one if you're doing business there.

Here in Florida a DBA is required in order to do business -- or you'll get fined (big bucks).