This one may seem like a tough question but the place I`d start is with your utility company. I`d ask them what it would cost to heat, cool, and light a space like this per SF.
If they don`t have the data, they should be able to direct you to a good source of information. Most likely department to have it would be their energy conservation unit.
Can I ask if you have your financing in place for this deal? :)
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Doug Atherton
Regional Vice President
Equity Corporate Finance, Inc.
DouglasA@equitycorpfinace.com
888-498-8999 ext. 109