Center Console Boats And More

purchasing a boat for lake and saltwater fishing, what is important to know about the motor etc?

We will be purchasing a used boat to use for lakes and saltwater. How do you prepare a boat for saltwater ? What do we need to look for as far as the motor etc.? We know we will need to buy a V hull for ocean, but we don't know much else. Any advice would be greatly helpful. We have never owned a boat before. we have however rented several times in florida. THANKS IN ADVANCE !