If the ground is very smooth with no rough uneven areas that force the tractor to slow down, I'd say it could be done in a day or less. I've got a five acre field that takes about four hours with a 7' sickle bar. The sickle bar will cut a lot faster than I can run the tractor. The ground is too rough to go faster.
It takes me about an hour per acre to mow our hay, and just a small amount longer to run the bushhog around the the pastures when needed to clip the lil trees and briars that spout up every two or three years or so.
"Nothing so needs reforming as other peoples habits." Mark Twain
With a bushhog I can mow about 2 acres an hour and believe me $30 is pretty cheap for an hour. It will take about $6.00 in fuel,,, I charge $40 an hour for a 30 HP tractor and people tell me that is too cheap......
Remember this, if you give the grass away you are contributing $36 per 4 x 5 round bale of nutrient away. The $36 is what I recently read was the amount of fertilizer in a bale. I no longer give surplus grass away and I have reduced the fertilizer expense tremendously based on the last soil sampling. Depending on the size of the tractor and the mower I can cut between 2 to 4 acres per hour. Each tractor will use approximately one gallon of diesel per acre.
I'd make hay out of it, but might not fit your situation.
$30 an hour seems cheap.
I'd think 3 acres an hour, probably better. Depends if he is a pro & has things sized right, or is just learning what he is doing & drives slow with a too-small tractor, etc.
He's a firefighter so he does this stuff as a sideline on his days off.
I can't make hay out of it, it's ryegrass that has gone to seed and is going to die pretty soon (weather's gonna get too hot for it)... I asked about that on here recently and the consensus was that the grass is worthless for hay at this point.
I can do my 12-13 acres of semi-smooth hayground with a 9' disc mower in about 3 hours.
We have 20 ac & about 11 is open but in 'patches'. Some places there's a lot of trees to go around, even tho it's mostly open. (Whinnyninny, yours looks sooo pretty )
We had a guy mow for us & charge $70 b/4 gas went so high, then once when it was maybe $2 gal & he did it for $100. Now we have an 8N w/bush hog.
Mother's Day, my request was to get to mow as much as I wanted (I LOVE mowing) and I did about 6 ac in 4 1/2 hrs. Kinda slow I guess.