The plan below won't cost more than $50 ($46 on Home Depot as of today)—when I first wrote this page it was under $40 (and when I used this plan a few years before that, it came out to under $30). If you build and store it right (out of the weather, with screws and bolts), buying the wood is a good investment. You can also use scrap wood and bring the monetary and ecological price way down. My favorite sukkah was in Seattle, made entirely of scrap, and it even had a window installed. The main thing of course is not the cost but the mitzvah! And nothing is sweeter than the mitzvah of sitting in a sukkah.

  
This is the sukkah frame I made according to this plan, still standing at Purim after a hard winter.

S'khakh: The most important part of a sukkah is of course the roof, made of s'khakh, which is not only the essence of the sukkah, but also the reason why it's called "sukkah". S'khakh can be made of anything that grows from the ground but is no longer attaced to the round, and it must be material that has NOT been manufactured into something new (i.e. not a woven grass mat). It should cover the roof by connecting two adjacent walls and reaching to part of one of the opposite walls.

The s'khakh should cover more than half the roof (creating more shade than light), but with openings throughout, and none of the holes in it should be bigger than a handbreadth. If you don't have enough s'khakh to make every square foot more shade than light, keep it sparser in some places but make the gaps smaller than a handbreadth, and make sure that you sit under the places that are thicker when you use the sukkah. (You can use also make the roof smaller by not extending the s'khakh all the way to the fourth wall, which just makes the part that's a sukkah smaller.)

S'khakh cannot be held together by wire or tied down. See below for more about why.

Even though most Sukkah dealers hold by the lenient opinion that allows them to sell rolls of bamboo slats held together by fishing line, some people (including myself) are of the opinion that that too is NOT kosher. Lastly, the s'khakh should not be attached in any way (imagine something like the roof of Findhorn for those who have watched "My Dinner With Andre"), and it should ideally rest on plain wood, not metal. It's a chumra that many people follow to not tie down or attach any of the beams or elements that support the s'khakh. The best way to make it super-kosher is to support all the s'khakh on freely resting slats, such as the 1x1's suggested in the plan above.

Walls: Without walls (2 plus a handbreadth) it's not a sukkah. Two full walls should make a corner (i.e., be adjacent and more or less perpendicular—but a circular wall or a series of small walls encompassing the same 90-degree arc is OK too), and the third handbreadth should come off the corner from the other vertical edge of one of those walls. The cheapest way to create sufficient walls is to use sheets or tablecloths (beautiful prints add a lot, too). People in more northern climes might want to add walls more solid than that – any plywood sheet will do, and something that comes up only half-way, or across only halfway, will still help keep the chill out. You might need to add another 2 x 4 upright in the middle of a wall to have something to attach a smaller plywood piece to. And if you really want to make it on the cheap and don't need a lot of space, you can save by going from an 8' by 12' plan to an 8' by 8' or a 4' by 8' plan.

The rule for the height of the walls is that they should reach close enough to the ground that a goat wouldn't crawl in (defined as three handbreadths or less), and closer to the roof (about as close as a handbreadth). The rule about the roof is more lenient if the s'khakh noticeably overhangs past the wall. In the plan above, the s'khakh sits on top of the 1x1's , which should be unattached but resting on top of the walls.