There must be a commercial real estate company to tell you what the going square foot rental price is in your area.
Without seeing it, I wonder what kind of driveway, parking, loading dock there is? Is it on a major street with easy access?
The whole building is available or is this just one area in the building? If one area, who are the other tenants and will they have a problem with a caterer in the building? Does the building and it's kitchen meet current codes, Will I have problems getting an operating permit (or whatever the equivalent is).
It's near downtown. Does that mean in a good neighborhood for catering close to businesses who might want a caterer or the near downtown area that no one wants to go near?
The kitchen sounds great but all the other factors would affect my decision on what I'd be willing to pay.
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.