Pros
Lots of new faces and people everyday. New co-workers every week.
You learn a ton of ways to interact with customers.
You can pretty much make your own hours.
You can wear whatever you want to work, they really don't care.
Cons
Employment offer is a joke. They'll either hire you without one, or if you ask for one it'll have a bunch of borderline nutty clauses, like you can be temporarily laid off as long as they want without pay, you can be fired at any moment no notice, but you have to give at least a 1 month notice before YOU quit.
No paid breaks, whether it's bathroom, smoke or lunch. Don't expect to be paid unless you're working.
Very high-stress environment, expect the owner to blame you for all his problems and mistakes. If inventory goes missing, expect a call from the owner days or weeks later saying you owe the money. Or if you mess up as a technician, expect to be paying out of pocket to replace whatever you break.
You have to be willing to say anything they tell you to say if you want to maintain your job. It's all about selling and making sure the potential customers are stuck with you at the end of the day.
Expect to work up to 7 days a week. Don't expect overtime, paid public holidays or anything of the sorts. None of it applies here. Your flat hourly rate is what you'll get paid whether you worked an hour or 100 hours in a week.