More people in the UK are starting up their own business fuelled by a desire to be their own boss and work in a field they enjoy. But more are doing this without giving up the day job. Side businesses are big business and generate an estimated £72 billion for the economy. One of the perils of starting up is financial, so having a full-time job to sit alongside a side business offers a steady income and security. But it also offers the chance to identify market opportunities, meet prospects and reduce costs.