I have an idea about services business. Just like Office-Support Service, it includes:

• Typing
• Filing
• Sorting Mail
• Entering Data
• Answering Phones
• Book Keeping
• Word Processing
• Spreadsheet Design
• Mail Receiving & Forwarding
• Databases
• Internet Research

Are just a few tasks an office-support service can perform to help out harried business owners. I want someone help me to create a business plan for this and guide me till start of business. I don't have enough funds to hire someone professional for this task. Anyone willing to help?

Some of those are basically impossible online. So the harried business owner hires an office manager to do them all, and 'general support services,' while common 30 years ago, are really not applicable now. Online bookkeeping, database management, and spreadsheet design, maybe. But with easier and easier software out there for the do-it-yourself business owner, even those are done in house, and the person who answers phones, types, files, and opens mail, handles all of them.
So I would say try it without getting into things like a 'business plan.' Just put yourself out there and see what transpires. Key to what you offer is your expertise and background in accounting, and knowledge of secure software, so that nothing is lost or hacked.

There are already such services in existence. If you need help developing a plan I suggest contacting score.org or sba.gov (if you are in the US).