It depends, unless if they have their own shops/business and are skilled which can do almost anything like opening safes, installing electronic locks, duplicating keys, programming car remotes or they get contracts with apartment complexes or businesses.
Locksmiths can make lot of money in many ways, but it also depends on the quality of their service and reviews that a locksmith is getting. It is the true that a good feedback from previous customers would increase the numbers of their future customers. People will definitely prefer the same locksmith and these locksmiths will be able to run a good business and earn a lot from it.
If youre looking for a locksmith near your area but dont know where to start, just visit www.autolocksmithfinder.com and search for a locksmith using your zip code. We highly suggest you to contact the locksmiths directly and get a quote. You may also visit www.remotesandkeys.com if youre looking for a replacement key or remote for your vehicle.