Maxon is perhaps the best-known supplier of these radios but Radio Shack has them as well. Don't expect too much and you won't be disappointed. Some neat accessories, e.g., headsets and ear-microphones are available. Recommendable, but only for that purpose. No license required.
Some assignments are good only during the day, others only at night.
Some are short-range and some can blanket the entire country, day or night. Hams do not normally communicate with operators in other radio services. Band segments are assigned by specific frequencies are not. The pool of technical knowledge among amateurs is great and amateurs are loosely organized in clubs. Many hams also specialize in performing public service, establishing communications links, monitoring weather nets, providing communications for public events, etc.