One place I saw an outhouse built into one corner of a outbuilding. If you didn't know it was there...
Have seen a couple of these also, they are called a "shed".
Been at several hunting camps that have them.
Storage in the front and the business end in the back, some type of drum under, think was an old 200 gal oil tank, with holes in it, gravel under/around it.
I have also heard of the "Alaskan buried Buick septic system", I would guess not approved most anywhere else?
Just what it sounds like, bury an old Buick and pipe it up.
I also found that there are several places that sell regular construction type Port-a-potties for use in hunting camps/vac cabins. (I guess I never though of this when I was dealing with my septic)
Found this out when I was asking about and purchased one ( $75 bucks, good shape) for my "Louisiana Box Blind" (home made hunting blind).
At "The Original Place" (travel trailer) we started out with a Port-a-potty, emptied it at the city park dumping station. "bout 5 miles away, also got our water from their well tap, used the public showers and garbage dumpsters.
What the heck, I pay my taxes.
As long as we were careful, and I watered the bushes, (always wondered why the grass grew so green on the back side of the deck), this would last about 3 days.
When company came, w/their own trailers, it was BYO-P'ers.
We then moved up to the "Sawdust toilet" ala Humanure style, this has (and still works) well. It's now the "upstairs toilet" for middle of the nite emergency use in the new and improved "Place" (cabin).
This still gets my top vote.
We now have a state approved septic, (land had a perc, on my list of requirements, when we bought the land).
Was about $3500
Out houses (actually, just a holding tank, that need to be pumped every so often) are allowed. I think min. is like 700 gal, approved tank. Neighbors have one, last them several years
I know of another house, close by, built with straw bales, solar/off grid, water from rain collection, wood heat that uses a sawdust toilet, has for quite a few years.
They have no plans to add a well and septic.