I need to convert our tutorial articles into videos (with English voice-over, 2 mins)

We are a software company mainly developing program tools fixing PC, mac or phone-related problems or music and video management tools. We have made many guiding/how-to tutorials like this: http://www.wondershare.com/mobile-phone/move-photos-from-camera-roll-to-album.html. Currently we are planning to insert a video for each tutorial.

Some requirement are stated as follows:
1. the videos will be like screen-cast-like videos based on provided problem-solving tutorial articles.
2. budget for each video is $10.
3. The length of each video is around 100 to 120 seconds
4. The voice-over is required and must be made with standard English (the freelancer needs to extract the scripts from the articles we provide)

We will work with freelancers who are willing to do the job for one video first. And then we can talk about bulk offers on weekly basis.