In regards to the employer/company is there a prerequisite, such as the number of years in service, etc?
there are no requirements that specifically address the employer/company. However, there have been cases where CIC has questioned whether or not the employer is "legitimate" - one person was asked to supply documentation about the business (e.g. business license, other supporting documents).
I would say - as long as the business is legitimate and and follows accepted business practices, then even if it is relatively new, it should be ok.