You are permitted to work for any employer while you run your new business, but it would make sense to do a job related to your business to help gain further business experience. You are not permitted to work full-time for an employer and neglect your business. Part-time employment is supposed to help you cover day-to-day living costs and initial business setup/running costs until your business is operational and making a profit. Your appointed endorsing body is supposed to guide and monitor you and your business so they will explain the process. Please note that I would not work for employers more than 50% of the working week, meaning that you give your business at least 50% of your time. If you abuse the visa route, your endorsing body can revoke your sponsorship and curtail your visa status.
