I'm not going to comment on legality, but if your service is targeting the larger companies, they will not do business with you unless you have a viable company

I'm not going to comment on legality, but if your service is targeting the larger companies, they will not do business with you unless you have a viable company. They probably won't do business with you even if you do have a company, but only employ yourself. Also with regards to your chances of getting a full-time job. That depends. Most companies won't have a problem with that, but some might. They might not look kindly on the time commitment they think you'll have to put on your own company. A company that's operating in the same field as your company obviously would not most likely not hire you, because of your competing interest.