Looks like something you could put a 2 man crew on and knock it out pretty easy. Depending on the size mowers you have, ie; production, the frequency you will visit this property throughout the year, and your actual overhead it seems like the price you posted along with the specs you gave for a mow, blow, and go service would be a bit high (everyones numbers are different). Something that you may want to consider with that many trees is the leaf clean up in the fall / winter, this could add significant cost to you. And I agree with Duekster, not all apartment owners are created equally some are horrible at paying on time if at all. Do your homework.