One week update:
First, thank you to all who provided advice earlier as it was very helpful. Second, to anyone who makes it through the next few paragraphs of bragging thank you again.
Today marks the one week spot and my nephew has done exceptionally well. I am happy to report that his ADHD is not nearly as debilitating as his father let on. Nephew is an incredibly personable young man, who focuses completely on the person he is speaking with and can relate conversations and observances back with remarkable clarity. He is splitting his time (living quarters) between my sister (his Aunt) and me, so we're both coming up to speed on living with a teenager and being responsible for another human being.
Sister was able to get him an internship at her company and is able to oversee nephew. All reports are good. Other than some minor professional advice along the lines of keep the cellphone in the backpack and stop checking it every 2 minutes, he has had a great first week and seems terrifically excited about his first foray into the working world. He's enthusiastic about everything: his work, the people, the project, the location and amenities that he has around him. He says he is thrilled to have work to occupy his time during the days.
He is not given a car. He carpools when staying with my sister. When with me, he uses bikes or public transportation.
So far, he's worked 10-12 hour days and then commuted 45+ minutes each way. As a result, he has been given no chores, other than cleaning up after himself, doing his own laundry, etc, which he did on his own with no input. From day one, he has displayed very courteous behavior and is very thankful about the opportunity. AFter meals, he picks up and rinses the dishes, each time without my asking. When going to the kitchen, he always asks others if he can get something for them. His clothes are neatly arranged in my guest room, and he pulls the comforter of the bed over the balled up sheets, but I'm not going to complain about how someone makes the bed -- it's great that he makes it! He's very kind and I think I have a lot to learn from him.
He returned to my house last night and was up early to take the train to work this morning. He's needed no prodding about getting his wardrobe ready ahead of time -- he's doing that on his own. My sister and I are both helping him plan his lunches ahead of time (sandwiches and batch cooking with crockpot). Not sure this part is sticking yet. I'll see this weekend when we actually cook something together - and shop for the ingredients. I may have him choose a recipe from budget bytes and then figure out how many days it will last, how many days he cares to eat it in a row, and then what to do for those other days.
My task this weekend is to help him learn how to budget. Any ideas on how to approach this? Should I sit him down and give a lesson, or work it into the food shopping for his crockpot meal? or just reference budget during all other activities? I really don't want to turn him off of it. I want him to see it as a tool to help him get what he wants out of life.
Another issue I'm having difficulty with is his relationship with his father. There seems to be much resentment from both sides of that relationship. Father has been treating his son like a lazy, incompetent moron and Nephew has been fulfilling those expectations. There seems to be passive/aggressive behavior and control through money. I think nephew is very astute to realize that getting out of the house was necessary and that he can now begin to move forward - even though he doesn't necessarily know where forward is.
tl;dr So my two questions relate back to whether to stick my nose into the father/son relationship, and how to incorporate a mustachian love for thoughtful spending into my young nephew's life. I'm considering the basic "1/3" method, just to keep it at a level he can grasp quite easily. What should I do?