Taking your insurance, mortgage, tax, and rent estimates at face value (I assume that these are fairly certain/stable), you might be a bit optimistic on your expenses:
- Vacancy: I don't know if 2% is the right number or not, but just to sense check - 2% vacancy means that you have no more than 1 week (on average) to turn over a unit, assuming it's fully occupied and each unit turns over once a year. If people tend to stick with longer leases (2+ years), this might be a safe assumption, but if everyone's on a year to year lease, this might go up a bit.
- Property management: do you plan to property manage the building yourself? Sorry if I missed the context somewhere in your post - if you don't plan to manage the building, you'll want to include those expenses as well. Even if you do plan to property manage, it would be good to build that scenario just to understand what your risk is in case you need to stop managing it on short notice.
- Maintenance: $1k/year - I'm fairly confident this is optimistic (or, at the very least, assumes a very short holding period after your renovation). Sense checking this, $1k/year assumes $125/unit in maintenance per year - if you call a plumber or an electrician for a unit once all year, you've likely exceeded your budget; this also doesn't include maintenance on common spaces for the building (although this could be wrapped into property management).
--> If you are hoping to hold for the long term, you'll have to budget for capex as well - you have to assume some lifecycle on major appliances - if your water heater(s), air conditioning, electrical system, etc. go out, you'll likely be looking at a >$5-10k expense for an 8 unit property
On the point about maintenance - while I feel confident that your number is fairly low, I'm not sure of the best way to go about estimating expenses on a small-medium apartment building is - I'm guessing it's a per-unit $ outlay approach or % of purchase price/year, but I think a more experienced investor will need to weigh in on this one.
Just double checking - how much cash do you need up front for the note + renovations?