Basic information applicable to all countries is available here. In some countries, additional conditions also apply – for more information, select a country from the 'Select Country Here' drop-down list higher up on the page.
In order to work in Sweden, you must have a work permit.
Read more about at Swedish Migration Agency on how to apply for a work permit or for a residence permit as a self-employed person or a visiting researcher.
More information about working or running a business in Sweden to be found at workinginsweden.se.