life in a fifth wheel with only one leg

AK or BK?

Honest answer will depend on your mobility level. I work in O&P and would be happy to discuss any particular concerns. You’re Prosthetist should be able to help as well.

Stock/cheap stairs are pretty bad even for people without mobility challenges. There are lots of options on newer units or ones that could likely be retrofit. To me, the biggest problem are the basic stairs with the floating bottom. The newer ones that sit on the ground are MUCH more stable. I have to think the steps into the trailer are the biggest problem. The ones up to the bedroom (or whatever is in the front) are much more stable and less in number typically.

Anything can be done. I had an Uncle with one leg. I can remember driving past his house one day and there he is on a ladder fixing a second story window. No prosthetic for him. He said he got around better with just crutches.

Don’t give up an inch! You can RV with the right planning and equipment.

No personal experience, but have a friend that has one , he doesn’t appear to have any more trouble than all os old people.
Frank

Assuming, you can climb stairs without great difficulty, shouldn't really need to do anything. Maybe look at where a strong handhold could be installed.

If stairs are problematic, you might consider a travel trailer. Preferably one that is low to the ground to minimize stairs.

If it's really bad and you incorporate a motorized scooter into your daily routine, you could consider a toy hauler (assumes you have someone who can open the loading door for you). Then you can just ride the scooter in and out minimizing the stairs.

You might consider one of these.
RV Lifts