I am trying to make a website user-friendly to blind people and would like to investigate the possibility of using something like Google's   text to speech service. There are two main questions

technology and how to use it (in simple terms)
financial and how that works

Basically the free service probably starts with your credit card and over 4 million characters (a month) of use you don't know how open is open-ended!

There may be much I can do with playing my own audio. the site is all about audio tracks - Stroud Voices

Any idea anyone?