Here is a tiny house that is being advertised for $2500 plus tax on Craigslist:
This really tiny house is halfway between a tent (it's much more comfortable) and a tiny house (it's vastly less expensive, and towable by most cars). Modular and portable (it weighs about 1200 lbs.), it has cedar siding, 3 huge screen windows, one large regular window, a single bed that's also a big lockable storage bench, and a table that can be used with the 2nd bench to make the bed into a double. I've designed it so that an outdoor shower and range/oven can easily be added. This model comes with a translucent fiberglass roof OR a heavy-duty (18mil) white tarp roof that unrolls on one side to create an awning (in the pics, the extra fabric is folded up above the door. Where the upper framing is open now, you can have either screening all the way around (I'd recommend this if you want it mostly for festival/summer camping use) or I can side it in cedar just like the rest of the exterior (you'll probably want that if you want to use it as a shed, or for cool-season camping. If maintaining the portability isn't important to you, you could add 2 4x10 sheets of 1/2" plywood as a base for a metal roof if you want to make it more year-round.
The tarp is 15x15, which means that it will fold down to cover the rafters when you want it to (there's a 1" gap on one side if it's all folded down), and that off of either the front or the back you can roll it out as 7' awning.
Because I wanted to keep this one as light and portable as possible (towable by a car), I could only use the one real window; it's like a charming, bright, comfortable cedar tent. If you need more security, you could get plexiglass cut to put over the windows when you're not in it. If you need it to be more for year-round use, I can make one like this that's got a solid roof, real windows, and is more weather-proofed and insulated, but it will be a lot heavier, and easily double the cost. . ..this also means that a third person will probably be necessary for setup, so there will be more cost in the delivery, too.
$2500 plus tax. Delivery, setup and modifications possible at additional cost. Setup is very straightforward. I can also add a counter with a sink in it (which you'd hook up to a hose) for another $100. Add a sawdust toilet and the shower and range listed above, and you're awfully comfortable as long as it's warm out.