You are correct - it is a good way to find some coins for your collection. Or, a good way to get cash to buy some coins for your collection.
I'll suggest a different path than those mentioned. I bought my first metal detector through Kellyco - Minelab Musky - still have it. Works great and I have no complaints. Good deal for $300 at the time. It is not a top end machine by any standard but in many it outperforms them. Good depth and dependable.
However, within a year after that I bought a Tesoro for my kids. It was one of their loan end models - less than $200 - like $160 range. It is also an excellent machine. Very light weight and very easy to use.
The Minelab takes a bit more to be proficient in the area of discrimination. The Tesoro is much easier.
If I were going to buy a new machine without question I'm buying one of the Tesoros. The one I bought for my children works well and for a beginner would be much better. They have several in the $500 to $750 range that have excellent depth.
As far as what you want on detector -- my opinion is to go for depth and give up all the "bells and whistles". You can buy detectors with little screens (IDs) that "suggest" what is under ground -- like a bottle cap, dime, quarter, ring, etc. You would be much better to buy a basic machine that does not have these features -- then you will actually learn how to metal detect. The ID might suggest a "pull tab" and in reality it is a ring and you pass it by not wanting to dig. Gold rings can show up as a pull tab.
As some told me once - dig everything and you will not be sorry.
There are several forums where you can do some research. Drop me an e-mail and I can point you toward them.
Again, many good detectors out on the market. You want depth over frills. Kellyco doesn't sell Tesoros - at least I don't think they do. Do not buy a detector from Cabela's, Bass Pro Shop, etc. You would be better off buying off of
ebay. If you can, find a local dealer that sells a wide range of detectors.
Good luck