Hello -- a bit late weighing in on this, but I've pretty much always lived in apartments, and I move around a lot (not really out of necessity, just because I like living in different places).
The leatherwork has to be a primary consideration when choosing an apartment, I think, in order to make the best of it. Ground floor is a necessity (one-story apartments are even more ideal) for me, and I rent an extra bedroom just for my workspace. I look for apartments with at least one interior room (no walls adjoining other apartments) to reduce noise pollution. Big walk-in closets with regular doors (not those collapsible track-doors) are also attractive -- I have cats, and being able to keep my hides behind a closed door in a relatively temperature-stable environment is also a necessity. If it's an apartment previously occupied by heavy smokers, or that otherwise contains weird, intractable smells -- no deal. I'm a smoker myself, but I don't do it indoors because I don't want my leather smelling like that.
I introduce myself to potential neighbors and ask them what times of day they'd be least-bothered by the noise, and plan my projects so that I can get the majority of my pounding done during those hours. I also let them know that it's perfectly okay to come knock on my door and ask me to keep it down, and I'm always cordial if and when they do. Never gotten a noise complaint yet.
If you don't mind a little reciprocal noise, you can ask the apartment manager if there's a block of buildings that's generally noisier or more noise-friendly than the rest. My current neighbor is perfect -- he blasts his bass 24/7, I'm hammering away at all hours, and neither of us mind a bit. We joke about it when we run into each other on the shared back patio.
So I guess my best advice is: Unless there's some reason you have to keep living in your current apartment, start shopping around. You can probably find a place in the neighborhood that better suits your needs when your current lease is up.
P.S. Living a floor above someone, unless you're in a steel highrise with concrete floors, makes being quiet virtually impossible. When I first got into leatherwork, I lived on a second-floor apartment sandwiched between a cranky old lady below me and bunch of (at least six) Brazilian college students above me. I was so determined to keep learning the trade and so conscientious about being a good neighor that I would pack up my tools and workbench every day and go do all my carving/chiseling in the park. Pretty much all I did at home was the stitching and finishing, and my downstairs neighbor still complained about how loud the squeaking was just from me shifting my weight on my feet so much.