1. I was a security guard for 3 years+.
2. How the job like will depend on the place you are
guarding. Generally to show security presence, act as the
company's walking security camera, enforce company rules, report
anything abnormal and safety hazards to supervisor.
3. At present, security agencies are in need of manpower.
As long you are trained and qualified, you'll get a job for
sure.
4. Security agencies usually will not care much about why you
want to be a security guard, whereas direct employers will
interview you like they do in any other job position.