Newbie looking for affirmation!

[Shannon Heintz]

I'm considering my first multi-family purchase. It is 2 4-plex buildings listed for $315,000. The property is clean, well-maintained, in a nice area of town (next to newer SFH and backs up to the city park) albeit a very small rural town. I haven't done the official inspection yet, but don't see any likely repairs. It was built in 1994 and all units are 2 bedroom 1 bath. The units rent for an average of $450/month and then there are additional rentals for garages ($130/month total) and money from coin laundry ($80/month total). All 8 units are currently rented. The property taxes are $7480/year and I estimate insurance around $1500/year. Using a purchase price of 300,000 and putting 20% down and after accounting for vacancy, maintenance, and property management, I'm coming up with a cash-on-cash return of ~20%. So that is good, right? Any reason that I shouldn't move on this? What am I missing?