If your avocation becomes your vocation, what will be your escape from work? You may grow to dislike toy trains. I've seen it happen. Not with trains, but with boats. We had a "boat guy" who loved nothing more than to be on a boat all summer. Then, he took an opportunity to take over the family marine business, and was surrounded by boats all the time. It didn't take long before the thing he loved became a chore, and the last thing he wanted to do in his time off was go boating. It changed his personality, he became unpleasant to be around, so much so that we stopped doing business with him.
If you really love toy/model trains, I encourage you to think very carefully about making them your means to earn a living rather than your hobby.
