Greenhouse

If I were going to build a greenhouse in Austin, I would make it just a small housing for seedlings...And so I would collect old windows people take out of their houses and give away on Craiglist...collect them until i had enough to make two similar size rectangles, then use recycled/reclaimed wood for the frame. I'd keep it small so that I can reach in and grab what i need and so that it didn't take much space. I'm still working on ripping out the rest of the yard to turn it into food space though :)

I agree with Jennifer T., that in Texas you can get by without a greenhouse. I have always wanted one but a higher priority for me would be a drip irrigation system. If I go on vacation in the summer, I come back and everything is dead and dry.
In the winter, you can grow spinach, chives, beets, kale, broccoli, chard and carrots- no need to wait for spring. Even if you don't have a greenhouse, you could still do individual row covers.
When I have shopped for greenhouses, I almost bought one from Harbor Freight. Sometimes they have coupons for a certain percent off one item. The kit I looked at is made out of clear panels that look like corrugated cardboard.
I love gardening, and my son is willing to eat vegetables that he helped grow such as purple carrots and asparagus.

The nice thing about living in TX is that you can garden all year long and do not need a greenhouse. I just built raised beds in my yard and grow EVERYTHING in them. I used landscape timbers and lined them with landscape fabric- you need to line them with something to keep the chemicals from leeching into the soil. Sometimes I will start seeds inside in late winter, but then I just put them in a sunny window. I don't do it often, though.

I am in the process of putting in my fall garden. Peas, beans, tomatoes (first time I am doing fall tomatoes) broccoli, cauliflower, cukes, salad greens, spinach. All of these are cooler season plants that should hold out until Dec. I also have an asparagus bed.

Good Luck to you and consult the county extension website for lots of good TX growing tips. Compost your kitchen scraps and get a good, sandy soil as most veggies like well drained soil.

L.-It really all depends on what you hope to get out of it. Building and maintaining a greenhouse really may be more trouble (and expense) than you are able to get out of it. Depending on where you live and the type of structure, it may require a permit and change your tax assessment.

Certainly if you plan on starting your own seeds it can come in handy, but without shade cloth and/or cooling system, it can become an oven during the hottest part of the Texas summer.

If you Google "home greenhouse" University of Maryland and Oklahoma State University both have great information sheets about all the things to consider.

Budget is always an issue, but if it weren't, and I were building one for myself I would definitely use metal framing in concrete footings/foundation. Rigid polycarbonate or fiberglass roof, wall, and ends. At least one side would be all sliding doors to really get a wide opening and plenty of ventilation.

Make sure water (and electricity) are readily available.

L.,
Kudos to you for getting into gardening. It's a wonderful experience. I use it for stress relief and to get more environmentally conscious/friendly. I host plant swaps every spring and fall and so perhaps by next spring, you can attend. Of course, I don't know where you're located. I'm in the Austin area.
As for a greenhouse, you can build one if your husband is good with his hands. My husband is a handyman (owns Ritter Renovations) and has started building me a greenhouse. A simple one would consist of framing posts and 2x4s erected once you know what your height/width would be, then you would attach corrugated fiberglass sheets to your frame. You don't even have to put a floor down if you don't want to. I have no idea what your budget is so I just suggested the cheapest version I know about.
Hope this helps and good luck w/ your gardening!
Jen