It's a legal/regulatory term so I guess the coldness is to be expected: https://www.investopedia.com/terms/a/accessory-dwelling-unit...
Guess it comes down to your target audience. If you're market primarily consists of landlords looking to make rental income, ADU seems to fit the bill.
Re:Modular Homes for Under $50k
by CyberDildonics on Wednesday June 30, 2021 @03:01PM
(#27692283)
I don’t know if you’re a non-native speaker, but there is actually a popular magazine called dwell - https://www.dwell.com/
I guess 'dwelling' and 'unit' don't have all those connotations to you?
Why not just say 'home'? Even 'Accessory Home'.