That can be grown from seed?
That go in the smallest pots possible
And another question, is growing legal plants for profit in a apartment realistic?
Look for alpine and rock garden plants. They are generally small. Also, African violets are always popular with apartment dwellers and they have several beautiful 'mini' varieties. Research is the key to finding both the popular ones that sell easily and the rare ones that have value to collectors.
As a hobbyist gardener, you might get way with having a plant sale once or twice a year, or even selling on ebay, but it's unlikely that it is legal to operate a for profit nursery out of an apartment.
pipsissewa tree Very elegant and some tree have been reported at over 3 inches tall. Well worth growing
I think moss rose is a pretty flower plant that can grow in small containers. It would also do better in a bigger container but I think since it has a small and shallow root ball, it may be OK in a small container that will basically limit its overall size. It is also advantageous to you because you can grow more from cuttings, not just seeds.
Speaking of cuttings, you could also consider plants that may look nice and big in a pot but it just really came from a cutting that has already rooted and will grow and thrive as a new plant.
Herbs are also something which you can grow plenty of, and people usually want herbs but didn't think to start it themselves.
You might be able to sell some plants in a kind of garage sale (or whatever they call it for an apartment) but garage sales are sometimes regulated by the city also, if your city requires permits for having one.
Another thing people like are arrangements of plants. You would be growing your own plants but by putting them in arrangements, you have a chance for a mark-up on those same plants that you would have sold individually.
As an example, maybe an 6" herb goes for $1 (using your competitive prices). But by putting 3 common herbs together in a wonderful and awesome arrangement, you could sell that container for $5.
This post was edited by gardenper on Thu, Apr 17, 14 at 23:21
Bonsai trees and bamboo fit those requirements. And if you need more space consider windowfarms.com
Here is a link that might be useful: small indoor hydroponics
I am going to guess that you specialize in baking pies. I just wonder whether you do fruit pies or vegetable/meat pies