That's a good place to start, I think. There are lots of groups online where people trade and sell plants/propagations.

You can learn programming in your free leisurely time, it's gonna help immensely.

I would reconsider this plan, imho risks far outweights possible profit. I knew a guy who sold plants (or better dried up parts of plants...). He made some really good money but got busted, obviously lost his scholarship and dropped out of uni.
When I was at school I did a lot of data annotation and moderation work. It is realatively easy (though you have to read and understand training maunals) and pays about 15- 19$/hour (these figures are from 4-5 years ago, might be more today). Especially good if you speak a foreign language.
E.g. im my case I did a lot of query matching, menaing you are presented with a search query and have to rate how well an advertisement matches this query in different categories. I worked with company called appen, but there might be other options too. Maybe take a look into it, they have a variety of different tasks (e.g. image annotation, recording voice samples, etc).
(Payment was via )

Depends where you are, but in Canada a part-time waiter or dishwasher job pays very good 15-20$/h. However as a long term goal, I would definitely learn programming. It is very fun and you can have a lot of freedom helping local businesses with websites or applications and even find a job relatively easily 25$ + /h (in Canada).

Maybe visit reddit