If in doubt, apply your own vacancy allowance (on a 6-plex, we would use 8.33 (1 month in 12) or 10% depending on the locale).Additionally, we never count the laundry revenue - our experience has been that if negates out the extra cost of the commercial machines, their operation, and upkeep  (others seem to like them).I can be of no help with the roof ... tiles do not like winter, so we have never encountered one.That said, it could be alright ... bring the rest of the numbers once you have them.

There would be spikes for vacancies/make readies, but some months would be really quiet. 

As to get real cash flow you must not only take in to account PITI but also capex, vacancy rate, and management cost.

Though the homes are in great shape, I get calls regularly from these tenants for maintenance issues, asking to pay late on the rent, etc.When you finally do get someone who trashes the place, the extra rehab cost and the increased vacancy rate begins to erode your returns.

I'm curious what some rudimentary formulas are to determine estimates on repairs, vacancy, etc.I'd love it if you let me know if anyone has shared anything with you!

But when you do get a vacancy, i would do what @Chris Winterhalter said.

Property manager (if you have one), periodic vacancies, any common area utilities, trash, misc fixes, reserves, etc. will suck up a lot of the rest.

Yes AZ and NV are cheaper than Cali, but AZ is unlikely to show you good returns and NV is likely to swarm you with vacancies.

To sum it up, a 7 year loan could have been paid off in less than 16 months, with a ROI of 25% for the bank, and I would still have been well off, and able to actually pay cash for my next property within 12 months between how the leases were written and how quickly I was(or rather would be) able to fill the vacancies!

In this market, with how low vacancy is, you are in a great position to have your apartment leased very quickly.