I don't want to spend lots of money for a HF antenna, and even if I did my apartment complex wouldn't allow it! This is my story, and while I'm no expert I hope that sharing my experience will help encourage others to try crazy things in the spirit of invention. A friend loaned me a Century 21 HF CW-only transceiver which puts out ~20W. As far as an antenna, I was limited to what I could build. I tried a bunch of different designs, including a trash-brew 40m base-loaded vertical, but it didn't work that well. I found that a "contorted dipole" (I heard it's officially called a zig-zag design) strung up on my ceiling works surprisingly well. I've only had it up a few days, but from Florida I've communicated with New York on 40m at 20W and Maine on 20m using 20W. Keep in mind that I'm brand new to CW, and that 90% of the conversations out there are way too fast for me to copy, so my greatest limitation is finding a CQ slow enough that I can respond to it.
The beauty of this antenna is four-fold. First, it's cheap (a few bucks worth of parts). Second, it's off the floor and out of the way (unlike my vertical antenna designs). Third, it doesn't require a tuner to operate once it's set up. Forth, it's virtually invisible! Seriously, if you walk in my apartment you'd have no idea it's there unless someone points it out.
So, will this fly for you? That's between you and your XYL. Measurements are similar to regular dipoles (approx. quarter wavelength per leg), but I cut these long and used an antenna tuner to shorten them until I reached a 1:1 SWR. Once the SWR was set, I returned my borrowed antenna analyzer and the resulting antenna network seems pretty stable!
The physical assembly involved a package of ceiling-mount (screw-type) plant hooks and a couple packages of 50' of picture hanging wire from Target (a few bucks total). The coax to the radio is pretty straightforward. Just a short patch of cable running up to the ceiling, then the shield goes one direction (to the 3 ground wires) and the center wire goes in the other direction (to the antenna elements). Both antennas are permanently soldered together, which is fine because SWR stays low and I don't have to jumper things around when I want to change bands.
Don't get confused by those coils! They're not used for the antenna!!! They're just there to help weigh down the wire to prevent it from wobbling due to the AC. Seriously, they do nothing, you don't need them. They're not even touching the antenna! Which reminds me, the two 20m radials were made from actual wire (because I had it lying around), so they're coated in yellow. No biggie! No reason other than convenience that I didn't use the picture hanging wire. Okay, that sums it up.
I hope this information helps! If you build a similar setup, let me know - I'd love to see it. If you have questions, feel free to email me. Remember, I didn't put much math into this - I just went with approximately quarter wavelength legs and started cutting them until the SWR was down to 1:1, then I didn't adjust it any more. It's been several days and SWR seems stable, so no antenna analyzer is needed anymore. Good luck with your project, and with any luck I'll work ya' on the band. 73!