The key fundamental lessons are still the backbone of personal finance today:Lesson 1: Pay yourself firstA key component: weather you make $100k or $1M the simple math should be the same.

An engineer sent by a cost segregation firm can find a lot MORE components to bonus-depreciate than you can estimate yourself.

I know a cost segregation study would be too expensive for such a small amount of property, but is it permissible for me to estimate the value of the components on my own?

I don’t think it’s one answer as with many things it depends. 5% is probably to high for a fully updated property taking into consideration the major components.

That’s my take on the critical components.

EXAMPLE: I haven't cut my own lawn in over 10 years because I can get it done significantly cheaper than what I make per hour.The other component to keep in mind is landlords typically hire PMCs for one of two reasons:1) No time to properly manage2) No expertise to properly manage- Note: if you have enough time you can learn the needed expertise.Everyone wants to focus on how supposedly "easy" it is to manage rentals.The reality is:1) The difficulty & required time increases as the property/tenant quality decreases with Class A => Class B => Class C => Class D2) It only takes one bad tenant, bad contractor/handyman or mistake that leads to a lawsuit to cost a landlord SIGNIFICANTLY MORE than the cost of a PMC.What Class of rental do you have?

The other three often don’t cover the full operating costs, so you lose money every month when one or more units are vacant.You also have more components that can break: 4 x appliances, plumbing, HVAC, water heaters—more repairs and more expense.The issue isn’t whether multifamily or single-family is “better.”

Keep up the good work.Most importantly, run a cash flow analysis and understand how to assess the life-left in the property's components (or assess projected CapEx expenses) based upon your findings on any subject property.Outside of operations, running numbers is essential to your success.

Typically these firms have some type of interior design component to them as well. 

As a small unit count LL, you may want to underwrite with a higher vacancy than the average vacancy for your area (underwriting should be conservative).even if a unit is brand new, when it is put into service the lifespan has started on every component.