If you bought second hand goods and resell them at a profit you are in business!

To be in business does not require you to register "Your Business" (Pty) Ltd

You can just be "You" for now and later give your business a name  and then just
be a sole proprietorship!

Operating as a sole proprietorship you merely need to open a bank account in your business name.
There is no need to register anything else.
If you want to trap the business name you can register a web site

When you just get started

You don't have to invest a fortune in stock
You don't have to give up your day job to get started

You need to Develop Your Skills

Marketing your products is key. Learn from books and other people!

There is no do nothing and get paid!
Scams Operate this way!