What could be a great hobby to have that is also good for making income?

How about making crafts..?

I think you should access and dicover all your skills, talents and passion first and start from there, one's good and profitable hobby may not work for you or for everyone cause it's not your interest.

Taking private tuition for the really needy people can be a good hobby while making some money. Many children though they are intelligent for some or other reason they fail to fare well in their academics. If you have patience then you can come to know where they are lacking and you can mend and make their lives! That used to be one of my hobby which I enjoyed a lot! Thanks!

Writing can be a good idea.

Mylotting for me.