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Put the age aside. Not even an issue! If you know your stuff in the natural medicines, put up your website and put out the word. You of course need to register your company and make it an LLC or Incorporated. You should hire a lawyer to register your business properly and to be sure that you have protected yourself from any liability. The credentials you put up about yourself that show you know about which you speak is essential. Read up and or subscribe to all the sites and reviews, magazines etc in your field. Post ads for your product wherever you can and where it is affordable. But and a big BUT -- Know your product, know your competition and know your audience/buyer/client. What are you offering that isn't already out there and ask yourself that question before you launch.
In answer to both your questions:
1.) Opening a new business (online or otherwise): In my state (NV), I needed a business license and was advised by my attorney to form a limited partnership, so I did both. In addition, I used services from Go Daddy to set up a website and from FedEx to print business cards. While my business (3D scanning, printing and training) is not online, I use a variety of online services. You can see more at www.clarketec.com.
2.) Computer literacy skills: In addition to general use of the Internet, you should probably have some familiarity with spreadsheets such as MS Excel and word processors such as MS Word. Other skills can be picked up at your local community college as the need arises.
Hope this helps and good luck.
P.S. 52 is young. I took the first of my 5 retirements at age 52. I'm now 77 and having the time of my life.