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No account is free. Its just that steemit pays the fee to create your first account you get through them, in exchange for information about you in order to avoid abuse of this service.

So can I convert it to paid account snd will this increase my steem power?

There is no difference between a paid and a free account once created beyond the resources that the creator gives you at the beginning and the initially assigned "trustee" (which defaults the the account that created yours). After creation you may add Steem, SP, or purchase a delegation if you need more.

Your trustee can also be changed by creating an order for it on the blockchain and then waiting 30 days, however this process requires knowledge of the CLI and is beyond the scope of the services that we provide.

Thank you for this valuable information. Just one more query does only adding steem into one account would increase reputation or it is really about the activeness and good content which will be liked by others? Thanks again.

A lot of it is about building a following, similar to any blog, but a little bit of Steem Power can definitely help you get started.

We also sell delegations, which are like a lease on SP.

Thank you for clarifying.