I might have a job mowing 200 acres twice a year and have some ??? How many acres can you cut with a 15ft or 20ft batwing mower in a hour? Also how many hp does your tractor pulling it have? The material onthe 200 ac would be medium to heavy grasses that are 2-3 foot tall.
Lotta questions...Answers vary according to how one question or another is answered....
People have been known to use 15' batwings with 50hp tractors. Ya gotta go S.L.O.W. but it can be done. To mow grass/weeds as you describe, and move along at a fairly brisk pace, you'd probably want 100hp at a minimum. You expect to go as fast as the mower is capable, I'd want 125+. Heavy grass is tougher to cut (and needs more hp) than brush in most instances.
Not much experience with 20'ers, but do the math......
Now, "How many acres can you cut....in an hour"? Does that acre have trees? Hills? Is it rough ground or smooth as a parking lot? Rocks? Houses nearby? (which may have youngins' who can [and will] contribute to "hidden treasures in the weeds" at a high rate of incidence.)
I've mowed as much as 10 acres (+) in an hour. (w/15' batwing) That takes 5-1/2 to 6 mph speeds, and VERY efficient use of your time. (ie Cutting WASTED time on turns) That's on carpet smooth clean grass fields that I know like the back of my hand. I've mowed as LITTLE as 1/2-acre (w/15' batwing) in hilly, slick (wet), heavily wooded, rocky conditions (along a river bank at that!)
And for comparison sake, I have a couple farms I mow that are "average" for around here (in mid Kentucky) One (190 acres) requires 36 hours with a 15' batwing/95hp tractor, along with 8 hrs for a 60hp tractor/7' 3-point mower. It is cut 3 times per year. 2nd job (215 acres) is 44 hrs with 15' batwing/95hp tractor. It's cut 2 times a year.
Not included in either is lowboy driver and service tech. Gotta pay them too, even if "they" is just "you".