I want to start with Technical Writing. I want to do this as a part of my leisure activities. I want to know how to start and how technical writers are paid.

Start with the Wikipedia entry on tech writing:

Technical writer - Wikipedia, the free encyclopedia

Note the link to the Wikiversity tech writing course which is a free way to learn more about tech writing:

Technical writing - Wikiversity

Good places to search for tech writing projects that range from very small to very large include the following:

Elance - Outsourcing to freelance programmers, web & logo designers, copywriters, illustrators and consultants | Elance

Guru.com - The world's largest online marketplace for freelance talent.

Rent A Coder: How Software Gets Done -- The most completed software projects on the internet

Both Elance and Guru work best if you're a paying member since the best projects require a paying membership. RentACoder lets anyone bid on anything, I believe. If you Google "technical writer" you'll find many other links of interest.

Vasily