The biggest cash flow killers are HOA and Property Managers so watch out for those. 

@Chirag Gulati the biggest single drag I had was having things not aligned to the strategy.

I see no incentive for him to contact you after you bad mouth him in front of 1,000,000 Bigger Pockets members.

They won't make money unless you make money, so there is incentive for them to help you best they can.

One of the biggest unaccounted expenses can be your personal time.

We've found this typically incentives people to stay in their units after an increase, as they have time to try it out to see if the new rates fit their budgets, as opposed to having to make that commitment to paying the higher rate for a full 12 months. 

I suspect this will be like solar panels if it even happens; credits and incentives to do it, but not mandatory.

That is an awesome incentive from your work!

My biggest setback is my income. 

You can attract some of those same tenants in outlying areas as well (think Nike/Intel)...biggest hurdles are future of landlord tenant law in Portland.