it depends on what your budget is....and what your style preferences are....i chose a 'house' shape for my greenhouse, and the largest one i could find in a kit, which was 12x24....its barely large enuf, and i always wish i had more room....it is an aluminum frame, twin-wall polycarbonate style, and i like it very much....harbor freight has a small one similar for only 800$, and of course there are many more in that style available for varying prices....you can spend as much or as little as you want....

Greenhouse Selection
 

jwharwell, I would suggest getting a greenhouse that is just a bit larger then you think you will need. I've filled 3 of my four shelves already, and It's not yet time for Cucumbers, Melons, and Gourds.

I'd also suggest to anyone thinking of building a Home greenhouse:

Attach it to your house. There are so many benefits of having a attached greenhouse. You can use the heat in winter to heat your house, and it will be easier to heat the greenhouse on frost days, as well as eaiser connections to water. I am deeply regretting not connecting my greenhouse to my living room, then I could watch movies, while planting.

I'm not sure it's orchids Marty grows in those domes.........