Six months. You can totally do it.

I trained for a 1/2 marathon in about 4 months time... but I was also training for a 1.2 mile swim and a 56 mile bike before the 1/2 mary.

I also couldn't run the last month before my Half Ironman... so I went into a 1/2 mary without even running the month before. Mind you, I walked most of it, but I was fine with that.

So yea... you can do it! GO FOR IT! Good luck!