Hi, my name is Nate and i have swung a metal detector before but just for fun. I am looking to purchase a decent metal detector that is somewhat waterproof and has decent depth. From what ive read so far a fisher f-5 is a pretty good detector. I have found one that is supposedly only been used a handful of times and is on its second set of batteries. What are some of the things i need to look out for as in condition/ operation to make sure it is working as it should from factory? and is this a good buy?