Does your father have his applicators license? Skid sprayer? You planning on spreading fertilizer with a home depot spreader?
I think you are grossly under estimating what it takes to maintain a property of this size. It is not a mow and blow job. They will want everything included - mowing, trimming, hedges, mulch, flower beds(changed out every season), fertilization, weed control, litter pick up, irrigation system maintenance/repairs, and probably snow removal also. How are you going to handle a freak snow storm that comes through and prevents patients and/or ambulances from getting to the hospital? You better have more than a shovel.