If you are new to this hobby the first thing to do is read all you can about detecting to understand what these detector can and can not do.
First thing is what are you looking for that is 24 inches deep, must be a very large item to be that deep. Also what is it made out off as a deeper item that are that deep probably iron .Most detectors we use for coin hunting will not go that deep in most ground, some get deep like 10-13 inches deep, but they know there detectors well and can do it with many little secret they learned from many hours of use. There is some on the beach get deeper target as I experience it a few years ago in NJ at the beach that was a new quarter at 13 inches deep, but with the sand it could have drop down when I used a sand scoop .
Been doing this since 1974 and do see many that watch some advertising of people finding lot of nice stuff, but advertising is not the real world as many will tell you. I have had several ask me for a detector that only finds gold rings and coins on the beach or parks, most detector will, but you have to dig everything including all trash to do this, but you probably have to dig 1000-1500 to trash items to do this. What you have to do is get to know your detector and what different items sound like and be able to tell large target and small ones. You also have to go where the items are as some find some good targets in farm field out east, but that is because this is where our country started and then bee a lot of people that live there and lost many items that are now antique and older .
Like I tell many if you think you can get rich detecting it is possible, but not probable as many that been doing detecting for many years will tell you that there is a lot of other hobbies you can become rich at. Detecting is a great hobby that you meet a lot of great people and you like excitement and some days you get nothing and the next you get lucky, just like fishing or hunting. To detect is great if you like surprise and doing your research to do better than those that seem to find it all we see in these forums
Sorry if I get carried away, but just want to let you know the real detecting.
Rick.