I don't need it to be all that fancy, but I need to design a guest unit for my house and don't really want to draft it by hand or pay for AutoCAD. Cheap would be good too.
Sweet Home 3d. http://www.sweethome3d.com/ I've used this program frequently to design living spaces, basement redesigns, tiny houses, and so forth. Here's a few examples from their website:
That's a neat program, but I already have the architectural design phase done and I need to draw up the construction documents for the permit process and so I can start ordering materials. Sorry for not making that more clear.
Have you tried DraftSight? There's also a list of alternatives to AutoCAD you can go through here: http://alternativeto.net/software/autocad/?license=free&platform=windows
I'm not aware of a free program that will give you the kind of performance you'll need for creating annotated, dimensioned, detailed drawings. One option might be to download a free trial of autocad or autocad lt. Just make sure you save a .dwg at the end of the trial, preferably down saved to an earlier version like 2010, and you can take that with you to whatever program you use next. Even illustrator opens .dwgs. for example. A free trial will likely limit the number of saves. Just consider that a good challenge.