In response to being able to collect EI while working, I came off of a Maternity Leave from a full-time job outside the home a year and a half ago. It COULD have changed since then, but as far as I know, you can only make $50 a week on top of your EI payment. If you make more than that, you have to report it to the CRA, and they deduct that dollar for dollar from your EI.

Technically you could stay on EI until you are full, but it depends on how fast you fill up and what you are charging - you may not be able to collect anything once you get a few children.