I am looking for some simple to build purple martin houses, any suggestions?
I took a look on the Internet for you and had no success. Try posting on the bird watching forum. I'm not sure, but I think you'll be able to get an answer.
Here is a link that might be useful: GW Bird Watching Forum
Mother Earth News published plans for one about 10 years ago.
Here is a link that might be useful: MEN Martin House article