how to build a Cheap grow room?

4 lengths of timber: 2 x 7 ft. , 2 x 6 ft. 1 x roll of clear plastic.

Sink the timbers, at minimum 1 ft, into the ground. Round off the corners of the posts. Cover the "structure" with the plastic and secure. The plastic will increase temp. inside the room.

Have the 2 big posts at the front to allow any rain to run-off.

we got a small greenhouse for about $50 new at a hardware store.