There are two completely independent issues here:
1. Technical competence with the 8051;
2. "Commercial" or "Business" acumen.

If you want to make a business of this, you will need both!

You will need an Accountant and/or other suitable professional(s) to advise you on the practicalities, legalities, etc, etc of setting up & running a business in your territory.

What sort of business do you want - manufacturing? consulting? something else?...

You will need to think about how you are going to market your products/services.

If you want to manufacture, how are you going to finance the initial development?

etc, etc, etc, etc,...