Here is a less expensive alternative to buying a green house, you can make your own.
Building a green house doesn't need to be complicated, this is a basic design plan and it was made for only $50.
Try to find old materials that can be re-used to keep the cost down for this DIY project.
You will need: PVC pluming pipe, fence post, pressure treated wood, steel T fence post, SPF wood, screws, rebar, nylon wire ties, utility wire, staple gun, 6mm plastic and plywood.
How To Build A 50 Dollar Greenhouse DIY Plans See Tutorial Here