I am trying to think of an area of knowledge or science that I can study extensively on the side.?

Question

What are some good ideas that don't cost a million dollars?

Answer 1

The one you love. Only you can see what it is.

Answer 2

This being the summer time -- why not think about studying plants, fruits and vegetables.

How do they germinate?  How long does it take them to germinate?  

What temperature/humidity conditions will allow them to grow bigger?

What types of soil, soil amendments and fertilizers help improve their growth?

Answer 3

Do you like astronomy?  That's one of the few scientific fields where amateurs actually can make a contribution to the science.  Lots of the people who discover comets and supernovae are amateurs.  You just need a telescope, and you can get a pretty good one for a few hundred bucks.

Answer 4

How to control your thoughts so know one can hear them. John S. PS I added you to my contacts.