I wanted to share some sites with you since it can be a very personal option of cost/finances that ultimately answers your question.
There are sites like http://www.odesk.com and http://www.elance.com where you can find a suitable person to type for you. This can be an “iffy” choice, as you don’t know these people and they can be anyone anywhere.
There is also the option of buying software that will type as you talk (Dragon Naturally Speaking - http://www.amazon.com/Dragon-NaturallySpeaking-Hom... this can be costly and it requires a little time to “train” the software too.
Most of today’s computers come with the ability to type as you talk. Look in your computers control panel/programs and features to see if your system has this ability.
There is the option of putting an advertisement in your local paper to hire through agencies, but they will charge you quite a bit of money to do the typing, especially if you want the work edited into a final document.
You have the option of having friends or family help you with typing – this can be the most cost effective choice.
Whomever you hire to type your book for you needs to be qualified and someone you trust. You would not want to give your work to just anyone.
Best of luck to you!