I'm not a total expert but have looked into this quite a bit for my own similar situation, it sounds like a sole proprietorship will be easiest and cheapest for your situation. I didn't end up taking the role for other reasons, so I don't have the practical experience of what you are describing. From what I've read, you definitely want to avoid having a corporation which is pegged as a "personal services business" (CSB) by the CRA, as this will result in double taxation on income (~30% corporate tax, and then personal tax on income paid to you as dividends.) Some of the common things which trigger the consideration of a PSB are a lack of owned capital equipment, and acting in a manner consistent with an employee of your client (for example having a fixed schedule for work attendance, using their equipment to perform your duties, not having other clients etc...
All this being said, it sounds like this is an excellent opportunity for you - don't let these concerns get in your way! I would set up a 1-2 hour long meeting with a local small business tax accountant for expert advice that could save you big $ over time. I recommend asking such things as which expenses will end up being tax-deductible, what kind of entity (if any) you should set up for your undertaking or if it should be done as a sole proprietorship, how you should structure your bank accounts for this project, how to avoid the PSB categorization, and what the bookkeeping and filing/reporting requirements will be for each option. If you can afford it, this will likely be a huge time-saver and a wise investment in your business. Good luck!
Disclosure: I have no affiliation with the accounting industry, or really anybody associated with it.