What kind of time are you prepared to invest in clearing this? 11 acres is huge for something that's under 4 ft wide. The walk behind tractor you linked says in the ad " The combination of a differential and larger wheels make this model more suited to mowing tasks than the G85, but this is still not a great choice for large mowing applications due to relatively slow working speeds (max. 2 MPH). If you are mowing several acres, a larger walk-behind tractor would be desired for a greater selection of working speeds (and also for steering brakes, which aid greatly in maneuverability, especially on slopes)."
For reference, my commercial ZTR with 6ft finish mower deck would mow about 3 acres per hour at about 7 mph (flat, fairly smooth lawn). The 26" wide rental that you linked is spec'd to handle .65 acres per hr by comparison, and that might be optimistic depending on how much brush, and how smooth/flat the lot may or may not be.
Clearing 11 acres of brush with a walk behind that's pretty narrow is going to take you multiple days. It might get a bit faster after the first time, but even regular maintenance mowing will take you a long time without large scale equipment. And good luck fitting it all in around weather conditions or real life stuff.
I think you're eventually going to want a real tractor for this property if you'll be doing any kind of frequent work or property maintenance. And it probably needs a 6ft wide belly mower or 3pt brush hog. You can probably find an old tractor with a brush hog on your local marketplace for about the same price as the walk behind tractor thing you linked.
If you have no interest in mowing this much property on a regular basis, you might be able to leave it alone and then find somebody to mow/bale it once or twice per season.