I have seen many sites which claim for typing but I doubt their credibility.

Do anyone know trusted sources on internet from where it can be done

 

Are you offering to type things for others, or do you need some typing done for you?
Where in the world are you? Shipping stacks of paper will be expensive.

 

I am offering to type for others.
In india

 

Search for medical transcription. There is legitimate "type from home" work in that area, that may pay enough to be worth your time if you live in India. There may be a requirement for a basic medical terms course for you to get the job. The way it works is doctors and other medical professionals record their notes on a voice recorder because they don't have time to write it down, or perhaps their hands are covered in human blood, entrails, and feces, then they need someone to type it for their records, maybe entered into a database. This is a fairly popular thing in the Philippines; some of my wife's family does it. You need good english skills and knowledge of medical terms, which is where the school course comes in. I don't think the course costs much or takes long, maybe a couple of semesters for the cert.