Season extension is pretty important for market gardeners and small farms so they can compete better with the global system shipping produce 1,000 miles or more from places where the growing season is year round. The rest of us can make sauces, dressings, relishes, pickled foods and dry hot peppers. Some greens can be grown year round in many places with a hoop house + row covers. Root crops store. Veggies can be canned or blanched and frozen.
I maxed out my seed starting space and then some so next year, I either need more grow lights or need to not start so many seeds. Maybe start maters and peppers indoors and direct seed the rest which in my case this year have all been cool weather crops anyway. I could have started those in a simple hoop house like Pete has as early as I started them indoors.
While we wait!
Augie's bean trellis/high tunnel solution
I think that Augie had a great quick and dirty high tunnel solution with his hog panel attachment to his green house. (Pole Beans in the summertime converted to plastic covered greenhouse in the fall! I would put more arch on it and provide 2 posts and a center support beam in case of winter snow load!)
The tractor store has hog feedlot panels for about $35 for a 3' x 16' size. Three panels arched over from a 4 ft fence and fence posts might buy a 8' x10' foot print? (another $50 maybe?) Basic 2x3 or 2x4 frame on the ends and a salvage screen door and cost of good 6 mil clear plastic? Gravel for the floor. $250 -$350 maybe? Cheaper than a shelterlogic solution.
If I were in the country I would try that, but I live in a suburb with image issues and city inspectors. (And it is a good place to live to tell the truth!)