That's very exciting @Filipe Matos ! I wish you the best of luck on this deal.
I'm not a Tenancy Act expert by any means but I did have to evict tenants from all three units of a triplex I owned when it was purchased by the local regional government. I gave 90 days notice and didn't find out until too late that 120 days is actually required (as @Roy N. states--of course!--correctly). But it really wasn't an issue. Luckily if it HAD been an issue, any legal fees would have been paid by the municipality in this case so I wasn't on the hook, but my point is that if you treat tenants with respect and dignity and give them as much notice / information / explanation as you are able, they will be more likely to reciprocate and you won't need worry about the intricacies of the Landlord Tenant Act. Tenants generally aren't legal experts nor do they want to waste their own time at a LTB tribunal (of course there are exceptions to this) so if you can offer some type of compensation or assistance in finding new placements, and treat them with respect throughout the process you may find it easier than using a more combative strictly legal approach.
Good luck!