In order to sue my employer, do I have to pay money (or a �retainer�) upfront, or pay for legal work by the hour?

No, often you don’t have to pay legal fees upfront.  I recognize that money is tight when you’ve been laid off, or you’ve been let go, and sometimes its better to not worry about every penny at the outset when you’re up against a well-funded employer and their lawyer. 
So in some circumstances I will suggest a structure to clients in which I charge a fee for legal work based on our success only.  In this type of arrangement, I will typically charge a percentage fee connected to the amount of additional money I have obtained through negotiations or litigation. 
In some cases I will even begin litigation (e.g. at court or at a tribunal) and work up until a point on this basis, prior to a hearing or trial and, while rare, in some cases I will proceed to a hearing or trial based on this arrangement. 
It’s good to get advice from an employment lawyer like me if you have work issues, you’re being pushed out or you’ve been let go from work.  Feel free to call me if you have questions or want to book a consultation.  
Wesley Jamieson
Wesley Jamieson
P: 905.572.5806