How easily can a Non EU citizen emigrate to Norway?

[Mensur]

How can they get a residency visa in Norway? Can they start a business there? What are the requirements to live and work there?

[treena.oakley]

You can find all this information on the Norwegian immigration page UDI. Generally speaking, the answer to your question greatly depends on 1. the country you are from (EEA vs. Non-EEA), 2. which immigration application you are applying from (ie: family immigration, student visa, etc..). Once you have legal residency in Norway (and are registered with the proper authorities) you can start a business/work, but first you must be legally resident.