OMG, a long list, @Joshua Thompson.Schedules C with zero income and large expenses, particularly interest, taxes, and repairsFlips reported at gross profit instead of full selling price minus cost of goods soldFlips reported as short-term capital transactions on Schedule DSchedules E with zero income and large expensesSchedules E with repairs several times higher than the rentMissing depreciationLosses from rental properties or K1s not showing up on 1040 (not always a mistake, but often is)All expenses grouped into some $40,000 "miscellaneous business expenses"Missing deduction for use of a business vehiclethere are another 20-30 very common errors and oversights, soon to include the missing 20% QBI deduction.

I also plan on installing key phob entry for the lobby, and some security cameras in the common areas to better secure the property and help the tenants feel safe.  

The biggerpockets.com people paid some lawyers to write up reasonable leases: https://www.biggerpockets.com/landlord-forms I've only looked at the California ones, but that one had not only leases, but common addenda, applications for the tenants, etc, and both PDF and Word docs that allow you to edit if you wish.

Run ROI scenarios. 

Run ROI scenarios.

Not that you'd expect to default, it's obviously the worst case scenario, but that is a whole heck of a lot worse.An alternative to refinancing is a line of credit secured by the property, a HELOC. 

(Then there is of course the follow-up questions- Other than yard maint/snow, garbage, utilities, etc. anything that's commonly missed that I can put on the Sched E?)  

Is that common for your area?

For those willing to do it I can't think of too many scenarios where a house hack doesn't make sense. 

Common expenses are higher - Trash, landscaping, lighting, etc2.