Hi Andrew,
So we jumped into this world not so long ago with mixed use 14 unit. I like the simplicity of the BP calculator too and use it. Good luck with this and I hope our experience can be useful. Apologies if this is stuff you have gone over:
loans: Most commercial loans won't amortize over 30 years, certainly if you are not in an LLC (and boy I sure would be with this and wouldn't want my other properties tied to it). So if you want to refi out keep that in mind. 20 years much more common and 25 still common but less so. Under 2M you may be able to get resets every 5 years with no balloon and you may not. YMMV and would love to hear. If you are figuring a 10 year hold factor in at least one reset when you run your rate. They tend to average higher so you are a little exposed there
vacancy/turnover: you may have the actual records but I'd up that a bit. Also turnover at that rent range likely to be high and refresh necessary. If you are paying property management they will likely charge for a lease-up fee (half to full month) on every turn in addition to their regular fee. Same for tenant placements. We have a turnover line item in our budget separate from vacancy. According to her records looks like you are already running over 5%. Offices have very long vacancies and really aren't that appealing to people in that context so I might up even more.
You will need to refresh apts.pretty often.
Capex: In general (not always) you will be dealing with less emotional, more experienced investors, so for instance if the roof is old or the windows etc factor the need to fix that into your projected sale price, since even if you don't someone will include the need to do so. I might add one time-based fix to your capex (i.e roof) in addition to the foundation and keep the same #
Flexibility: You will have to be attentive to permits and immediate repair and will have more scrutiny than on single families. A complaint will draw the relevant agency far faster with a multi like this, so be prepared...you will be less likely to phase in a repair over time for instance. If the fire department or BOH takes a notion things can get ugly quick, so don't cut corners (this advice is repeatedly ignored by all of us, which is fine till things go south). Anti-discrimination, lead issues, etc. All are under much more scrutiny and you don't necessarily get assumed to be a good guy. Snow MUST be cleared immediately, side walks etc.
Insurance: seems low, I might double that, but you should be able to get a quote. Having an umbrella/liability policy a must.
Other: random taxes and permits I'd check, as well as the method of commercial taxation, and whether they bump it up on purpose. She mentioned electric and didn't see that there ($100/month for common areas perhaps?). We have wifi in our Western MA multi for 75 a month and offer it free to tenants as an amenity and that seems to be a plus.
Maybe this is the biggest one: $2200 a month for the gas guys from that one apt is a huge part of your return How stable is that? I can't imagine its truly long term, or is it? Put that at regular rents and you are likely break even at best in cash flow based on my quick scan. That could be a nasty shock.
Hope this helps.