Scott, the best approach for sewage disposal for your situation is to install a sewage vault, and have the sewage hauled to a sewage treatment plant when the vault is full. This is the most ecologically sound, and economically feasible method considering the very limited use the cabin will receive. Your family, and guests can control the cost of maintenance of this system simply by being very conservative in using water. Consider posting a sign in the bathroom over the toilet, “If its yellow, let it mellow, if its brown, flush it down. JWA