One big problem with taking this job and then carrying a weapon (and let's assume it would be a handgun rather than a knife) is that if you were found to be carrying, it would probably mean getting fired on the spot.
That in itself creates another problem. When you apply for the next job, your potential employer will probably ask for an employment history. You may be asked why you left your last job, either on an application form or in an interview. So what would your reply be?
To be honest, you would have to say you were fired for carrying a weapon which was directly against that company's policy. So do you lie and say you didn't like the job or simply wanted a better job? What if the potential employer calls your former employer and asks for a recommendation? They may find out that you lied, and if they don't like guns either, the chances are that you won't get the new job.
None of this may happen, but it
is something that you should consider.
As to carrying a concealed weapon, don't even think about it until you have been issued a CCW. If you would ever get caught by an LEO, the chances of getting a CCW much less legally being able to buy a weapon could go out the window.
I have been told that there is very little to worry about in terms of getting held up, which is why the security is so lax
If the company told you this, I would raise a really big BS flag here. The papers seem to always have stories about armed robberies at convienience stores, gas stations, and drive-thru espresso stands, all of which have little or no "security measures" other than cameras (even if that). She may be trying to put your mind at ease about not getting held up but the fact remains, places with little security are usually targeted by robbers before others.
Look at banks; nobody at a bank is armed (other than some places that have armed security guards) and banks typically have policies against employees carrying weapons. In any event, a robber with a gun will come in with it at the ready. Once he points it at you, you are going to be at a disadvantage until the situation changes so you
could draw a weapon and defend yourself.
Like a bank, check cashing places has cash on hand to do business. That makes them a potential target by robbers.
Tough decisons to make but plese keep the future in mind.