I completely agree—there are many ways to integrate good design into a more accessible space without increasing little to any cost. As long as you stay under four units, you're not governed by the Fair Housing Act, which has some accessibility requirements. Just to clarify, ADA requirements generally apply to commercial spaces or federally/state-subsidized housing, while accessibility requirements can apply to both public and private entities. I often use "ADA" as a blanket term, but that can be misleading.
I've made my Unit C (part of a three-unit property) more accessible, but it's not ADA compliant, nor would I claim that, nor am I forced to since I'm under 4 units. However, it can now better accommodate someone with a disability, and they can add any equipment needed to further improve accessibility. For instance, I didn’t install grab bars in the shower, since more penetrations can lead to more failure points based on my experience. Instead, I installed a curbless shower, which required fully waterproofing the bathroom. Helps with wheelchair access, but was more costly to waterproof the bathroom and not just the shower.
Exciting reads if you so choose:
https://www.huduser.gov/portal/publications/destech/fairhous...
https://up.codes/viewer/california/ca-building-code-2022/cha...
Cheers!