You must be a Canadian citzen to join the Canadian Forces. If you obtain Permanent Resident Status and being ex-service you could try this route but it is not very successful:
Information for Non-Canadian Citizens
Canadian Forces (CF) policy states that in order to be eligible for enrolment into the Forces, applicants must hold Canadian citizenship. The only exception made to this policy is as follows.
Applicants who: are not Canadian citizens, but do hold Permanent Resident Status; and possess specialized skills / qualifications the CF has need of and cannot fill with a Canadian citizen; and do not pose a risk to any national interest; may only be enrolled into the Canadian Forces if permission is granted by the Commander of the Canadian Forces Recruiting Group (CFRG).
Application Procedure for Non-
Canadian Citizens
As you do not currently hold Canadian citizenship, you will have to be granted a Citizenship Waiver by the Commander of CFRG before starting any of the selection testing. In order to do this you must provide a curriculum vitae (CV) or resume to:
Canadian Forces Recruiting Group Headquarters
Attention: SSO Selection
Canadian Forces Base Borden
PO Box 1000, Station Main
Borden, Ontario L0M 1C0
The CV / resume should include:
Personal Information
Name (in full)
Date and place of birth
Brief outline of where you have lived (include dates)
Where your immediate family is currently residing (include parent, siblings, spouse and parents-in-law)
Reasons for your relocation to Canada
Date of arrival in Canada and date, you were granted Permanent Resident Status
Education
Name of all educational institutions attended
Grade / Level completed and year of completion
Diplomas / Degrees awarded
Areas of specialization
Marks / Grade Point Averages
Apprenticeship / Journeyman qualifications
Employment
List all part-time, summer or full-time employment positions you have held
Dates for each position
Brief description of duties for each position
Qualifications or training you received “on-the-job”
Activities
List all volunteer positions you may have held
List all clubs / organizations / community groups you have belonged to
If there are any other points, or pertinent facts you would like to include, please feel free to do so.
Once you have submitted your CV / resume, it will be assessed by the Headquarters to determine what skills you possess that may be of benefit to the CF. Once this assessment has been completed you will be contacted directly and told whether or not a waiver of your citizenship has been granted. You will not undergo any of the selection testing until you have been granted this Citizenship Waiver.
So I wanted to be in canada and also join the army. Just wondering if you got to be a Canadian Citizen to Join? And also is there an age limit? 
