@David Hildebrandt congrats on the property! A few things to add. First off with your partner being a dentist, I'd be more interested in the cost seg on the dental office than on the 8 unit and SFR. Dental offices are some of the best properties out there for cost seg since there's a lot of specialized plumbing and electrical systems not to mention all the FF&E. Depending on the specifics of the office there could be a lot of value for him hiding in there. Now since he's a dentist I'm assuming the passive loss limitation will come into play (unless he happens to be married to a RE professional) If he makes over $150k passive losses are disallowed and would carry forward.
From my calculation the basis in the buildings should be about $239,540 ($325k purchase price and about 73.7% improvement value - $185k improvement/251k total) so depending on the details you could see $24,000-$72,000 reallocated as @Yonah Weiss noted. With that basis you're looking at $8,710 depreciation per year with the regular straight-line method. ($239,540/27.5 years = $8,710)
I'm assuming the $2,000 to $2,400 per month is your NOI after taking out all expenses other than depreciation and debt service leaving you with $24k-$28.8k annual income. The straight-line will bring that down to $15,290-$20,090 taxable income per year. Since this property was acquired in February 2018 100% bonus depreciation applies, you can elect to do 50% or not use it but that's a question for your CPA. Generally you'd want to take as much as possible so you'd do the 100% bonus depreciation.
So let's work out what that'll do for you and your partner. Let's say you're right in the middle of the 10%-30% range at 20% reclassified for about $48k of 5 year and 15 year assets with $192k remaining 27.5 year assets. On the remaining $192k you're getting about $7k depreciation per year for the full 27.5 years. In year one you're getting $55k total depreciation ($48k+$7k). If passive losses are disallowed and you're carrying it forward you'd zero out taxable income for several years before seeing a positive taxable income again. Year one: $24k income -$55k depreciation = $31k loss, zero taxable loss carries forward. Year two: $24k income - $7k depreciation - $31k carry forward = $14k loss, zero taxable loss carries forward. Year three: $24k income -$7k depreciation -$14k carry forward = $3k taxable income. Year four and after: $24k income -$7k depreciation = $17k taxable. So with this carry forward you're paying no tax first 2 years, a little tax 3rd year when the carry forward runs out, and then back up to a little higher than where you were with straight-line in year 4 and after. If the limitation doesn't apply then you could get a refund if the loss zeros out the rest of your income and the benefit would be a one and done type of deal for the current year.
The benefits aren't huge on a property of this size, but they're definitely there either way. Just up to you and your partner if it makes sense to spend $2k-$3k to save $7k-$10k on taxes over the next few years. And thanks for the tag @Michael Plaks!