Mortgage terms in Canada vary from 6-months to 10-years with the 5-year, fixed-rate financing being the most popular (but not necessarily the best).You will come out ahead in the long run by using variable rate financing - there have been analytical studies comparing fixed-rate versus variable over the interest rate history from post WWII until present days which produced these findings.  

Do you have any strategies to predict the rehabbed value accurately ahead of time?

WATCH OUT... don't get stuck.. some rights people can't sign away (ahead of time) and you'll be in court trying to defend why you moved all of Joe Blows stuff out, re-rented the apartment while he was lying in a hospital in Italy while on vacation and came home 10 days late to find he'd been robbed....

Organized: they should have the processes in place to handle most anything on their own, reports should show up monthly automatically and anything far from the norm should have a heads up given. 

Me personally i would not fix anything in the house now. it will be a burden for your grandparents that are still living there. plan ahead and have the money and the contacts ready to move in on the house as soon as you can (i also hope its no time soon) but being ready should reduce the downtime for the house. and when the rent starts to come in you can use that to pay of the rest of your loans. let your money make the money you need to pay the loans... 

I'll probably go ahead with it as long as everything else looks good.

But I like plan ahead as well :)

The interest will cost you about $8,600 over 10 years.You can over pay and still come out $3,600 ahead!

She understands that this is my vision and goal, to get through this first deal above/ahead is all i could ask for.

If you find one before you do that then you're ahead of the game.