A social business is set up primarily to serve the community rather than to make money. One of the problems with such a business is that as serving people is the primary motive it is easy to forget about the fact that it needs to work as a business in order to survive.
This link will take you to a series of webpages from the Welsh Government that will help you work out if your idea of a social business will actually work from a financial standpoint.
The majority of this information will be applicable to anyone in the UK. However, if you live outside the UK or in a part of the UK that has developed a different legal system to the rest of the UK you will need to check if everything is appropriate to your own situation.