Always look at multiple properties.
1) whatever rate they are asking, no matter how good, is too much.
2) NEVER trust their measurements. You only should pay for USF (usable square footage). So (pre YOUR build out) if there are pillars or support walls, you have to subtract the space those things take up. Also whether it's 50' or 52' matters. Take your own accurate measurements and compare.
3) Longer is better 5-10 years is best for initial lease. And do it in terms of months (60 months, 120 months) and put in options if you can at already negotiated terms)
Also, it's a NEGOTIATION, it's not a compromise. Know the difference.
Example of compromise:
Lessor: We are asking $30 per square foot, NNN.
You: I'll pay $25
Lessor: I can do $28
You: How about $26?
Lessor: Done.
Negotiation:
Lessor: We are asking $30 per square foot, NNN.
You: I'll pay $25
Lessor: I can do $28
You: How about $24, 60 days rate abatement for buildout?
Lessor: The lowest we can go is $26, not sure about rent abatement
You: How about $25 and you pay for all electrical and plumbing
Lessor: How about $26 and we'll include all electrical and plumbing... but no rent abatement.
You: $26, all electrical and plumbing, and 30 days rent abatement.
Lessor: Done.
And most negotiations will take a number of weeks, unless they only have one property.