Hi Lisa,
Welcome. First we need to know where you want to listen with your scanner. There are several types of "digital" signals and you will have to match the scanner to what you want to listen to...for example if you are in a place that uses P25 Phase 1, all of the newer scanners will work. If you want to monitor P25 Phase 2, the list of devices narrows to a few. There is also NXDN, Provoice, DMR, and on. As far as cheap, they are not cheap and the newer they are the more expensive they are.
I just found your other post where you listed what you want to listen to and it's P25 Phase 2. There is also DMR, LTR, and NXDN in your area--yes, lots of letters there. Start with something like a Uniden Homepatrol 2 or a BCD436HP. Enter your zip code and agency categories you want and it'll get you started. After you get the hang of things, you have the option of personalizing it and adding to it.