A good rule of thumb to go by Manidip, as far as your first site or two, why don't you choose something in which you have some good knowledge on and can offer some good content about it. You will enjoy it much better to if it's a topic your somewhat passionate about.
Also, if that isn't an alternative for you, then, perhaps PLR content will help you.
PLR or (Private Label Rights) content is articles etc. that are prewritten on a certain subject that you can use for your content.
Mind you, you should not use PLR content in it's original state. You should change and rewrite the articles so that they moreless become original again. This will get you past the duplicate content issues imposed by the search engines. Re-write the articles a good 50% or so and you should be fine. Some people say 30%, some say 20%, but personally I would go for more.
Not all PLR content is created equally though. Some of it is very poorly written, and well is just garbage as far as the articles are concerned.
PLR Pro, is considered the #1 PLR Content site on the internet and I have to wholeheartedly agree. There is also Article Underground which is very highly regarded as well. But, these memberships cost quite a lot of money so it's probably not an option for you.
I think in your situation if you were going to go with using PLR articles I recommend our good friend Guido's new site. Guido is a member here and he has a very good new PLR site as well. It is free to join, with limited access of course to some of the features, but he offers great value in the free membership, and his paid membership is very well priced as well.
Check out Guido's site here
PLR Niches. Also, knowing Guido as I do, I'm sure he will help you in any way he can.
Cheers
Davin
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