A greenhouse is a serious hassle. It takes up space you might not have in excess. It's expensive to build, furnish and maintain. It needs tending and cleaning. You have to sacrifice trees for it, and still worry about hale, icicles and falling branches. Keeping it clean is a constant challenge.
(Ours is 10 years old, and needed serious serious repair to the roof. We realized that when a young raccoon wandered into the house one night.)
So, if you intend to undertake such a project, you must have a very good reason to want it. And you need to think about how best to take full advantage of it. What do you desire? What can you grow? How much can you consume?
The first couple of years, we crammed it full of tomatoes, peppers, cucumbers and eggplant, which grew enormous, but didn't produce well. Turns out, you have to invite, even entice, pollinating insects into you greenhouse. Then we had chronic, pernicious white fly infestations. The mail-order ladybugs all died, either en route or shortly after arrival - ants did a better job. Had an outbreak of powdery mildew - and disposing of diseased leaf-litter can be a problem. Cats got in and took advantage of what they saw as indoor plumbing. Had to keep refreshing the soil in the containers; buying earth by the sack. And when it went well, we had so much produce, we couldn't preserve and give it away fast enough.
It's a longish, steepish learning-curve, different for everyone. One thing I can tell you up front, though:
There is no substitute for early, thorough research. Do your math!
