Kits for under $1,000 would probably have to be modified to deal with the wind. Where in CA do you live? We had a bad windy storm in this area this winter and I think the winds were in the 65-70mph. range. There were a couple of society members who had damaged greenhouses and someone had a friend who's greenhouse completely went down causing a lot of damage. Mine is one of the sturdiest I've ever seen on cement footers so it's not going anywhere. But, it was a lot of $$.
Whatever you go with make sure it's on footers, a foundation or something that will make sure it's anchored to the ground. Unfortunately pressure treated lumber, steel/aluminum aren't cheap and polycarb. isn't either. If you price out your framing and covering materials you may find that you may need to budget and save for a while longer. Especially if you want one that's a decent size.
I always recommend you look into your zoning building codes before thinking of building a g.h. or buying a kit. Most kits on the market don't have engineered plans and won't meet the requirements of my county, for example. Many counties in CA are very strict about size, construction and wind load requirements. I had to get engineered, stamped plans and it wasn't easy dealing with permits. Some things to consider..