I have a greenhouse, but it is not set up yet. To do so, I have to take down a fence that I am still using, cut a few trees, take out the stumps and machete hack out a snarl of green briars. So it's not on my #1 list...... but I found a good deal on it and snagged it. it is a high tunnel type, maybe 30-40 feet long and got it on Craigslist for $50.
I have one...I keep exotic or tropical plants in it for the winter. There is a furnace and auto watering system. In the summer most of the plants go outside into the gardens or on patios.
It is 15X26. We cover itt with 2 layers of plastic to hold in some of the heat. It is now running for 30 years. We love it. In the past we had a table and chairs in there and had brunches with friends....fun days...