We do a fair amount of single tenant NNN properties that have long term leases to national credit tenants. Generally they're either Absolute Net, NNN or NN. The absolute Net one's like Walgreen's means they're paying absolutely everything including the building structure and roof. Most NNN leases the landlord is responsible for the basic building structure but frankly on a brand new building very few investors are worried about the walls collapsing (and if they do, that's what insurance is for) It's the NN leases where the landlord has some maintenance responsibility (typically parking lot or HVAC, something that will likely require some capital outlay during the life of the lease) that things change a bit. Sometimes it's a reserve for replacements of $0.10-0.20 per square foot which is deducted from the income to arrive at a slightly lower NOI. Other times it's reflected with a cap rate that's 10-20 basis points higher. I've seen investors handle it both ways, but typically the former.
So bottom line the NOI is what it is and it typically includes no expenses, and no vacancy and collection loss (on a long term lease to a national credit tenant) The cap rate for an absolute Net vs. NNN might be slightly lower, but probably so little as to get lost in the noise. A NN vs. a NNN should either have a slightly higher cap rate to reflect the greater risk to the landlord of having to shell out some cash for whatever their repair and maintenance responsibility is, or an explicit expense deduction for reserves. Investors don't care about NNN expenses as that's all on the tenant. If the tenant wants to protest their taxes to try and get a lower amount, that's probably going to be on them. Frankly with a build to suit project I can't imagine the operating expenses would vary by that much except for the property taxes and utility costs. If Walgreen's wants to be a particular corner it doesn't really matter who develops it, the property taxes, insurance, utilities, etc. aren't really going to change.
As far as multi-tenant properties, you might have some tenants who negotiate their CAM charges below what they should actually be charged in which case either the landlord eats it, or tries to pass it on to the other tenants (who probably won't pay if if they've got a good lease) We just appraised a large shopping center and between all the different reimbursements from tenant to tenant the landlord was collecting about 85% of their total chargeable operating expenses. Mostly due to some of the anchors not paying increases in CAM or less than their fair share of property taxes.
Some clients have requested we show the reimbursements in the income and then cancel it out with the actual expenses, either way the NOI is the same and on a single-tenant NNN lease, that's all the typical investor is looking at.