Ensure that you do your research before you contact a contractor to build a greenhouse for you. You should have an understanding of what you want to grow and how much of it you want to grow. You should also know where the best place to put the greenhouse will be. The contractor can't help you if you don't know what you need.

Remember that permanent structures over a certain size will require a building permit. The exact dimensions that require a permit will change from town to town. Ask your contractor what type of greenhouses he or she offers that won't require a building permit.

Make sure your contractor doesn't have to outsource for materials. The best greenhouse contractors will have materials on hand to help reduce construction time. Hiring a contractor who doesn't need to go to a third party for materials will save you time and money.

Make sure your contractor can give you a reasonable estimate of time and money. Greenhouses can become very expensive as they become larger and more complex. It is imperative that you know how much money you can expect to pay before you even get started on the project.