Question: How to evaluate commercial property?

[Paul Singh]

I am a currently an Owner/Operator of a Gas station but do not own the property. I have been there for nine years and recently my landlord has given me the option to purchase the property from him as he wants to get into other ventures. On the property is my gas station and fast food restaurant with a combined rental income of $6000 a month. This does not include property taxes and/or CAM. The purchase price will be between 700-750K with a 20% down @ 20 years. I am not sure yet of the expenses and have not adjusted for vacancies( I don't foresee any vacancy due to the fact that i have been here for the past 9 years and the restaurant has been here for 12).

My question from the subject line is "how do I evaluate commercial property?" What are the values I should look for to figure out what is the current value of the property, what will be the value or appreciation of this property 10-15-30 years down the line?