What is the best online business startup for someone with little cash to invest in it?

EBAY.

i think, you can build websites and do internet marketing or you can do option trading. if you know nothing about them, you can do the courses first or reading the text books.

This is a little bit like answering the question, 'how long is a piece of string'. There are so many possibilities - where to begin...

Okay. With the right skills, you can make money with a very little outlay indeed. Build a site (or blog), get people to visit, sell other people's goods (e.g. Amazon) - aka affilate marketing. Or you could sell stuff you already own on Ebay, and beging to build an Ebay business; pay to surf (or read emails) programs are also possible (again) where you earn money simply by surfing and filling in surveys etc - agloco.com is a good place to start, here. Etc.

It all depends on the skills and determination you have.

There are probably thousands of opportunities. If I were to recommend just one, I would (and do) recommend Dr Ken Evoy's Site Build It!.

SBI! enables almost anyone to build a website that gets traffic by creating unique and personal content. It comes with tools that show you how to step by step build such a site. Also, the site that you create is one that you're interested in, even passionate about. And hopefully your passion comes through and you end up creating a niche site that people keep on returning to.

And once you get regular visitors to your site who enjoy visiting it, then monetizing the site, via Google Adsense ads. or affilate programs like Amazon is not too difficult.

SIB! also includes a fantastic, informative and helpful forum of other Site Build It! owners that serves to encourage all through the inevetibable ups and downs that come with online business.

There is more, and this free guide to Site Build It! tries to explain the 'more' through articles and videos, http://www.site-buildit.com , but that would be my tip.

(SBI! costs US$299 per year, but there is a 'nothing to lose' money-back guarantee.)

Consulting might allow you the chance to bring in clients while working on getting new clients. What are your skills, interests and passions??? Which of them are wanted or needed by people who can afford those products or services??? All you really need is the money for a business license and the determination to succeed.