Can you find out what the current tenants are paying per month? "All in monthly" means utilities included?
So 5000 per month for approximately 2000 square feet means about $2.5 a square foot.
In a city the size of Toronto that would seems appropriate but again I would check on the average going commercial rent.
After a quick google search..
http://www.commercialtoronto.com/Information/rent-calculation.html
I found this link with a calculator for commercial rent in Toronto. Too much to retype here so I tried copying the link.
Allen Mayer is the broker whose picture is on the page in case the link won't work.
According to the page, there are other factors to consider like the landlords TMI -Taxes, maintenance and insurance that are all added in to the rent. Also office and warehouse space are calculated differently. I don't know where your situation fits in to that.
The prices stated on the page are significantly higher than what you talk about.
Given the various factors involved as explained on the site, I would contact a local broker for a more involved and accurate valuation. With general building condition, lease issues and all the other factors stated on the page, it would seem more complicated than it first appears. You may be seriously undervaluing the property.