Would you be reluctant to hire someone that had their own business?
Firstly, is the position full-time? An employer will want 100% of your skills and effort dedicated towards their business, and may be (misguidedly) wary of you poaching clients or work from them for yourself.
Upon hiring you, some companies may ask you to sign a contract which will state that you cannot work in that same field while employed there; i.e. No out of hours work.
They may also feel that you are only going to stay a short time until you've garnered more skills or until your own business takes off. If this is the case, they won’t want to put all of the required time and effort into training you, only to have you stay for just a couple of months.
If it is a casual or contract position your odds are a bit better. The company can’t really expect you to work just for them and it should be okay for you to find additional work outside of their requirements; e.g. Run your own business.
If you want to become a fulltime employee of another company then you need to customise your CV and information to match the client's individual requirements, highlighting all of your skills and abilities that fit that company's style of work. Unfortunately, a lot of businesses won’t want to employ someone who is too ambitious and running your own business puts you at the top of that list.