If lightness of playing is a serious reason to consider nylon strings but otherwise you want a steel string guitar, I suggest you get a steel string guitar and the lightest steel strings you can find (extra light) and put on it (the first or high "E" string should be about .009 or .010 inches rather than the standard .011 or .012). By the time you wear them out, you will have built up callouses and you can switch to regular "Light" strings which will give you more sound. If you put nylon strings on a steel string instrument, it won't harm it but as Jack says you may get discouraged because of the lack of sound.