We've had a variety of RVs over the years. As those years progress, we are finding the need to ease the access, as it were. The bed is particularly important.
In 2015, we downsized from a 27' Class C with a walk-around short queen to a 24' with the "east-west" slide, the Sunseeker 2250. We are both in our 60's and while we were younger we enjoyed the overhead bunk area in our pop-top camper and our 21' fifth wheel. My wife is alter-abled these days, so she's simply not able to climb into an overhead.
At your age, you'll probably want to start in the overhead bunk if all else is suitable with the unit your are looking into, but keep in mind someone will be crawling over someone in the middle of the night. I've done it hundreds of times, but certainly don't prefer the practice.
A motorbike on a trailer is probably no issue for a single rear wheels. The bigger issue is capacity. By the time you load the unit for yourself and lovely bride, then you'll need to determine what you have left from the Realistic Cargo Carrying Capacity (RCCC) and Gross Combined Vehicle Weight Rating (GCVWR). You'll probably find you will be at capacity or above.
Personally, I've never seen a single rear wheel axle on a Class C; they can be found on Class B and some (somewhat misnamed) B+ units.
Our C on the 4500 Chevy chassis has a GVWR of 14500, if I recall, with a 5000/500 lb hitch. The unit is more than capable of towing at those numbers. I don't recall right off hand the GCVWR number,
We didn't want a slide, but decided to try one over having something longer overall. So far, with proper maintenance, this unit has been trouble-free. Here's the floorplan:
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We have a 6" two-piece dense foam mattress as well others with this design. The halves are angled at the junction, so we have never had an issue with feeling like we were "falling in a crack" or being rolled to the center. The bed is a full queen, so my feet no longer hang over the end unless I want them to.
Hope all that helps!