I’ve owned a BMW bike for the past 11 years. It needed routine maintenance every 6K miles, including:
-valve clearance check/adjust
-throttle body synch (each of the two cylinders had its own throttle body)
-engine oil change
-gearbox and final drive oil change (every 12K)
-check various things for wear/trouble (brake lines, pads, etc.)
This service typically cost about $300 at the dealership. If you bought the bike from the dealer who is servicing it, they may give you a loaner bike to ride home while they service it; if not, you’ll need to arrange your own transportation home (and back to the dealership to pick up the bike).
If you get a bike with overhead cams and shim-under-bucket clearance adjustment (most sportbikes), the adjustment is more tedious/expensive, but the inspect/adjust interval is a lot longer, like 18K miles.
I use sport-touring tires, which generally last about 6K miles. If you buy them over the internet and change them yourself, you can get away for about $300 per set; if you pay a dealer to change your tires, the grand total (parts+labor) will be closer to $500. Harder tires are available that will last more like 15K miles; the compromise is a slight reduction in available traction, but I know people who have no complaint about this. Sport tires go the other direction: lots of traction, but you’ll be lucky to get 4000 miles out of them.
My bike was shaft drive, which is just about maintenance-free; as noted in the maintenance schedule above, I only needed to change the lube in the final drive every 12K miles. If you get a chain-drive bike, the chain needs to be squirted with lube every now and then (~500 miles?), not a big deal. If you get a Harley it’ll be a belt drive, which is paradise: truly zero maintenance.
Apart from that routine maintenance, I didn’t have much trouble with the bike, i.e. I wasn’t farting around with unscheduled maintenance/repairs all the time. In 135K miles it only needed to ride in the back of a pickup truck once, and that was my own fault (fuel line popped off inside the tank because I hadn’t tighted the clamp enough when replacing the fuel filter).
If your bike does end up disabled somewhere, you don’t need your own trailer. There are plenty of towing services out there who are able to carry a bike to the dealer of your choice; indeed, as Alpha Twit notes, motorcycle dealers often have that capability themselves.