OK, I am trying to remember a paperback I read back in the 70s. The plot was very disjointed, so maybe it was one of those books written as a spoof by multiple authors who did not communicate with each other, like Naked Came the Stranger or Atlanta Nights. All I remember is that the protagonist was just called "The Boy" and it starts out with him living in a shack which is up on stilts in a swamp or at the shore. Something happens (maybe his mentor dies?) and he has to leave, so he climbs out through the trap door in the floor and heads off to various adventures. I know this isn't much to go on, but maybe it will spark someone's memory.
My memory is that this was a relatively new book (two or three years old) when I read it around 1978. It was in English and I think published in the USA. Also, it was an adult novel, rather than young adult, but I don't think it was "adult" in the sense of being erotic.
In response to further comments, I will add that I don't think there were any supernatural / magical elements in the stories. I think it was a standard after-a-global-disaster world. War? Plague? Famine? I don't remember. I also don't remember any geographic details, but US is probably most likely. This was all 35 years ago...