I'm going to assume you mean the
B7800 since the BX series only includes 1500/1800/2200/22. And the only mid-mount mowers I know of
are finish mowers. If you go with a mower that hooks up to the 3-point and the rear PTO, then you can go with finish mower (either side or rear discharge) or a rotary cutter (also known as a brush hog or shredder) that does a little rougher job, but will cut brush and saplings. Can you leave it on all the time? Certainly, but you may not
want to because you'll have to watch the sides of the mower to make sure you don't run it into something, and you will have less ground clearance; no problem on fairly level ground in the open spaces. Slopes too steep? You might consider a tiltmeter from R&B Manufacturing if you'd like to know just how steep they are. And when in doubt,
back up the slope, go forward down the slope in 4WD, and don't try to go across the slope. No one (including me) is going to tell you exactly how steep a slope you can go across because it can vary with the way the tractor is equipped; i.e. where the center of gravity is. Generally speaking, it shouldn't turn over up to 20 degrees, but 12-15 degrees is my personal limit, and if you go to the maximum, just remember that one tiny little bump (stick, rock, etc.) on the high side or one little soft spot on the low side, and over you go.
Regular maintenance? Look through the
Operator's Manual at the dealer and you'll find what needs to be done and instructions for doing it. Basicallly, it's changing engine oil & filter, changing or cleaning air filters and fuel filter, and changing hydraulic oil & filter(2) and cleaning a strainer (screen), and greasing the grease fittings on the front end loader and mower.
And while we'll be glad to answer your questions on this forum, these are all items you also want to discuss with the dealer if you're looking at a new tractor.