When you arrive at Canada specific question (finance, regulation, taxation), there are active Canadians here on the site who can field them.As for finding a group of investors in the TO area, give a shout to @Gary McGowan who holds monthly REI meetings to see if you might be able to drop in.

If it is just for your own usage just make sure it is permitted to do so then do what you need to do and do not register it with the city until you are ready to sell it so you can avoid a higher taxation and re-assessment of taxes. 

What I would ask and I think will be useful for everyone on BP is to share some good sites/maps on which one can see up-to-date Sale prices (not listing) and rents as well as utility expenses and taxation for the US, so we can all have easy access to how each market currently is and can do quick decision on where to look at for maximum profit. 

It's a good thing for the public these contracts have come under various new regulations to curb the predatory types.Option contracts are under some new changes as well, not understanding these contracts can cause a taxation nightmare, mess over a seller and as you asked, the results can be harsh, especially on the operator who got a seller in a financial loss. 

Flipping houses is considered a business, and when a tax-exempt entity engages in a business on a regular or repeated basis, UBIT taxation applies.  

As I was thinking about taxation issues on real property but still I don't get any connection.

While much if it has universal application, there is a distinct U.S.A. bias, particularly in the areas of finance, regulation and taxation where things are a little different here in Canada.Rest assured there is a considerable cadre of Canadians here who can assist with any Canada specific questions.  

Additionally, flips are considered inventory and therefore excluded from capital gains taxation (both short and long).

The only way to do so would be if you utilized an installment agreement to pay over multiple years. and in some cases they can be disallowed as a disguise to avoid taxation in the current year; however, that does not happen very often.

As you mention, holding RE in an IRA has other benefits - no income tax until distribution, no capital gains tax at sale (if no leverage in place for 12 months).