B.M.
Like one of the others to respond I have a Verizon family plan now, that I am very happy with, but I had a Tracfone prepaid when I lived in NY. If you are sure it will just be for emergencies, I think pre-paid is the least expensive way to go.
You can pick up a phone at Wal-mart (or other stores, or directly from the website, you can look around). I went to the website to activate and buy time. It was around $120 for a year of active service and about 1000 minutes (I'm not too sure of the details, since it was about 2 years ago). The phone worked well (again, in NY, but I have no reason to think it would be different here) and I never had any issues.
If you do go prepaid, you can get montly minutes, or you can go longer term. I would suggest the longer term, so you do not have to add minutes all the time. You do not risk your phone not working when you really need it.
Good luck.