Unless you need the liability protection or have very high income, the overhead in Canada of having a corp is very costly. Hiring an accountant to file corp taxes is usually over $1500 a year alone, then you need payroll, etc. Then you're also paying double tax on that income with a corp. Corp receives income and pays corp tax, pays employee (you) you pay income tax.

If you have a small side project with low risk then I recommend sole proprietor for sure.

In any case, soon as you start generating income you need to track income/expenses, register your business, register for HST and setup a separate bank account. I think TD here charges $25/mo just for that privilege.

So yeah, sometimes a fun side project loses its excitement when your stuck doing paperwork and start adding up the expenses, it's not worth it.