Blogger.com is partner with Adsense that;s why Adsense accepts blogspot blogs but only best blog's. A blog which must have a lot of quality contents, traffic and something important for visitors. Then Adsense will approve you.!
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Yes I am using free domains like blogger and I am earning adsense from it but its only take me very few money ..It works but I guess you need to work very hard to make an income out of free blogger
You can make money with any free sub-domains as long as your blog's content doesn't violate the policy. The content should be unique and has good visitors.
Make a blog with rich content and quality then google adsense will approve you, with any free subdomain.
Yes, it works really fine. Try to use it if you can. Yes, ofcourese, it works with co.cc. But always remember, the more useful, legal and original your contnent will be, the more you will earn with adsense.
NO, If you are from Asian countries. Google Adsense already changed their policies for new account approval for Asians. but once you got approval you can put your ads in sub-domain too