Personally I do not know how to precisely calculate this but it would definitely be worth some investigation.

Evan in the post above had a more precise method. 

Question --is the five year mark calculated with any precision?  

If you need more precise data RentRange is a good place to go.Good luck.

While the CRA does its best not to precisely quantify "substantially renovated", other builders and accountants have indicated the bar is somewhere between 60-70%.The good news, like any business, if you collect GST/HST on your sales, you can claim input tax credits.  

BTW--I have ended up in legal fights with borrowers (one to be precise) that ended up without any loss of principal, but ended up not collecting on all interest due under the note.

That's a no-no for rentals precisely for this reason.

You could also contact a realtor and have them do more precise comps.  

Warren Buffet says when evaluating intrinsic value "it is better to be generally right than precisely right."

Your CPA can help you with the precise calculations for that investor.