how do u figure out the monthly or yearly rate to lease space

Very broad question, you should contact a local broker in your area to help you. Depending upon the type of space your leasing, there will likely be things like CAM fees, Net charges, etc. This question is too broad to answer without more information about what your trying to lease. Contact a local commercial real estate broker in your area to help you.

Try checking all listings of similar building size and location in the city where your building is located. It will give you a good start. match as close to your building as possible.