Uhh what?

Premium ships are the only ones that cost actual money.

Normnal ships are unlocked through leveling..

what i mean is...... im asking if the nxt ship that will be unlocked is free of charge if im gonna use immediately......

The game will inform you when your BO is high enough level to unlock a ship.
Then you can select it in the ship tree.

Just remember you can have only one line on one BO so if you take Hosho you cannot take Junyo ETC.

There is no other way of unlocking ships.

ok...... am i going to purchase b4 i unlock the ship?(the money is not in premium, from the game only)......

First unlock it then you can buy it at the harbor for credits.