When you get ready to buy one(greenhouse) check out the Greenhouse Forum they are a wealth of info. Sorry can't help on the Poinssettas, this is my first year.
Paws

In the trade, it is usually agreed that most poinsettia growers don't make any money on the crop, but use it to pay fixed costs over the fall/winter, plus keep some of their employees so they will still be there when they need them in the spring.
Having said that, if you are a GREAT marketer, you may be able to custom grow special things and make a little money.
Since you don't know where to get cuttings, I am assuming you are not getting trade publications where there are often ads for such materials. Belonging to a greenhouse or other growing association would be a help also, to make contacts and find out about the challenges of growing poinsettias or any other crop.
Good luck, but do some research before jumping in. Heating for the poinsettia season is expensive, more so than heating for a spring bedding crop season...by three times, in my experience.
Ann

You might want to try something other than the following: poinsettias, mums, pansies, easter lilies. The big growers and the big stores have that market all covered up as far as I can tell.

Yeah, SKIP the Poinsettias... I used to be a grower in Iowa. The fuel will kill ya'! Besides, they are a big pain to grow...not for the beginer..
You need to focus on growing things that are very seasonal- as in not needing much heat, more just a head start in spring. Just shut the house down in the worst months. Over the past 10 years, many many small Greenhouses have gone out of biz in Iowa. That is why I moved to Texas. You might perhaps think about growing perennials...start your seed in spring and grow them on. Let them winter in the cold house with zero heat. Then, the next spring, you will have everything blooming for sale, not just green packs.