Hey Ellen, Joel has given you some good points to check into. I analyze commercial properties for my firm and these are the main factors I consider. Let me know if you would like a copy of my analysis spread sheet, happy to share it.
Add: Annual Rent
Less: Vacancy & Collections allowance (Anticipate the building having a vacancy at the end of the lease and work you way backwards to see how much you need to allow for) - 2%-10%
Less: Prop. Management Fees (NNN should cover but always confirm) - 3%-6%
Less: Yearly accounting and Legal fees - ours are around 2-3k
Less: Asset management fees ( we allow for this because we need to make sure the property is looked after for our passive investors- food for thought) - .5%-2%
Less: Structural Reserve (yes sometimes this is in the NNN but I don't expect that the tenants are going to reinvest as much into the building long term as I would expect, as well at the end of their lease you can expect that they won't want to cough out anymore than they need to. Allow for it either way) 1-5%
Less: Debt Service
Less: any other fees you may incur that NNN doesn't cover.
What you have left per year is what you should compare against your investment to determine Cash on Cash return.
I don't trust anyones future CAP rate projections, run your numbers based on what you already know.
I hope this helps,
Warren Marshall
Sundance Realty & Management