I actually just did a job like this, but at an assisted living facility.
The area is 30x80ish - 12 yards is about the average laid done every year.
The area itself is a PITA for weeding, it's all open...3 bushes, but is built on a swamp, so shitton of weeds.
We just put down commercial grade greenhouse fabric (I would use a pond liner the next time) and went overtop the existing mulch (not my decision) and used #1's and #2's on it.
We brought in 6 wine barrells, filled with $250-$300 of annuals and done!
Used about 33 tons of rock. Took 3 men, 1 machine, and 2 tandems 8 hours to complete.
Definitely a job that pays nicely, if they want to pay for it...who cares? Make it worth your wild!