I am looking into getting my first bike since I have been A little kid. Mainly will be riding on rails to trails at first and hopefully get into some simpler single track. Looking for a great first bike that I won't grow out of too fast, but when I do I can easily upgrade the parts. I also, don't want to spend a lot seeing I am new to the sport. Don't want to spend over 650. I am hoping someone could point me in the right direction for a bike. Oh, and I know I at least want a 29er!