It really depends what your hair is like. My hair is very coarse, thick, and straight. I don't own a hair brush and haven't for years. I use my fingers to "brush" it every once in awhile-a habit that started when I used to wear my hair very short. I don't get tangles because of the type of hair I have. I also have a very sensitive scalp, so when hair stylists go at my poor head I have to stop them. Despite what everyone says..you'll get dreadlocks..etc..I have what I call tv hair because it doesn't require much maintenance to look good, and it takes a huge amount of effort to mess it up. So..I guess my answer is: If you have hair like mine, don't worry about it. :) I also grow my hair really long to donate, which is when I start seeing tangles (last time I cut off 15" and there was still plenty for a nice hairstyle)
If you don't brush your hair then it will be knotted and will be very hard to make it straight.
Can you say dreadlocks
It would get nappy