"Someday you will have to sell this car."
Translation:Kiedyś będziecie musiały sprzedać ten samochód.
Kiedyś będziecie musieć sprzedać ten samochód - souds tottaly odd! should be: Kiedyś będziecie musieli sprzedać ten samochód.
yes, I don't know if there is a rule for it, but two infinitives sound terrible.
Why wouldn't this work? "Kiedyś będziecie musiały ten samochód sprzedać" Does it sound weird?
It's possible, but it's not the usual word order. You rather put the verb first and then its object.
I think the first comments make this clear. For the "polish ears" two infinitives sound bad.
Not sure what happens if three are needed, though :) But perhaps in regular speech they aren't.