I had a really negative look at the night-life side of Hollywood, which I really didn't like. I went to New York to focus on modeling, and then of course found that New York was not any different from Los Angeles. ↗
If each of your time steps is one week long, you are not modeling the stock price terribly well over a one-week time period, because you are saying that there are only two possible outcomes. ↗
The problem with interest rates are that you are not modeling a single number, you are modeling a whole term structure, so it is a sort of different type of problem. ↗