After several years of selling small plans on the Internet, my business is starting to do pretty well this year. Don't expect to make a bundle with this one plan but it could grow into something larger as you add other garden related plans and projects.
If you don't already have a traditional outhouse plan go to my site below and then to the discussion group. Do a search there on the term outhouse or privy. I have a link buried somewhere in the discussion posts to USDA site with plans for (among other things) a government approved outhouse. The plan can be printed out on-line.
Hope this helps.
CountryPlans.com