for 20K, i would say, remote control unit. remove ya from the machine to standing around watching it, with a remote control in hand. good chance remote control unit has tracks, vs tires. so you gain some traction / flotation.
as soon as you put a human on unit. everything changes to accommodate the operator.
as soon as you attach controls to unit to "walk behind" the unit. you are at the mercy of the machine, and how much you really want to walk. along with slip and sliding under machine on hills and in wet spots.
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some of the SKID STEERS, might be an option. more so the smaller units. everything fits out on front. and can turn on a dime.
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with MossRoad posting. you can see a "power trac" unit. were all attachments fit out on the front. much like a skid steer.
attachments fitting out on front, i only bring up, due to being able to accurately see what you are mowing easier, and any tall weeds get taken down first, so you are not covered with all the dust, pollen, water, mist, etc... from mowing down taller weeds.
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2 wheel walk behind units, you can get sickle mower heads vs rotary mower decks for them. that more likely be in 40" range.
you might be able to connect "sulky"? i hope i got term right, a little dolly per say you latch on behind 2 wheel tractor, and you stand on it, and 2 wheel tractor pulls you around on the dolly errr sulky. and do what ever you have attached to the front end of unit.
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atv and/or UTV pull behind mowers, they generally have there own "motor" on them. you can get either finishing mower or a rotary mower setups. many of them allow for "off set" and being able to swing them all the way out to one side.
there are various "lifts" that can be added between atv/utv and what ever you have on behind. to help adjust height and lift stuff up off the ground. to deal with hills, ditches, bushes, etc...
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with others 40" trails, on 50 acres. to much micro managing, time to start opening up the trails and like to wider paths, and using larger tractor and wider tractor to get stuff done.