Are you looking into poop? Imagine a little house, complete with a flush toilet or two. It needs to be on property which legally accesses municipal sewage or a private septic system.
Poop flow: Remember to examine poop flow! Where you place the house and toilets actually impacts flushing. If you are located downhill from the sewage lines, then pumps are required to get there.
Poop flow defies gravity

See toilets inside a home, using gravity to flush. Then notice the grinder pump, installed outside and underground. It is the key to flushing success, creating pressure that drives waste uphill and to a municipal sewage connection. (AA Public Works)
Poop pumped: Fortunately, anti-gravity plumbing challenges have been met and solved. Make sure to install macerators or a grinder pump, for little house peace of mind. Check out these (clean) options below.
Poop gets broken up & pumped

Here’s a macerator which connects to one below-grade toilet, while hidden behind a bathroom wall. (Saniflo)