I used a training book for my full marathon that was for 6 months from walking to a marathon. My dh has recently started running and his first half is in April. If you take it easy, listen to your body, don’t add more than 10% increase in mileage per week, and take walk breaks as needed both in training and in the race, there is no reason in the world you could not do a half marathon in 6 months. You can do this!
Earlier this year, I was coming back from a 3 month layoff and a hip injury. I started all the way over in late April – early March. We moved mid-March so it was a slowwwww start. I went from that to a full marathon competitive with my three runner pals by the first week of October. It can be done!