Don't worry about selling coins/treasures. Silver will go for 10% under melt where I am, and copper coins, unless rare, go for nothing. There won't be a line up at your door for every wheat cent you dig. Enjoy the hobby, but don't go into thinking you are going to be making money from every dig.
I got lucky one time and found a copper artifact which I sold to museum. I was using a $425 dollar detector, the artifact was worth more, but in all my years detecting, that was the only find worth "big" bucks. I am not saying this to be a dick, just letting you know that most stuff you dig, including coins are not worth a ton.