tl-dr: With perfect aspect, current/ongoing state is ambiguous. In your sentence, the time phrase may condition our view of the ongoing state.
I would interpret your original sentence as follows: at the point of retirement, you may or may not own one car, but you won’t concurrently own all three (in that case, you would have used ‘will possess’.)
Perfect aspect does not say anything about the current/ongoing state – that is the domain of the continuous aspect. Thus current/ongoing state is ambiguous, although we may infer something about it from the situation or other factors. For example,
I have owned a car.
It’s not clear if you currently own one, but we can infer that you don’t, because otherwise you would have just used the present simple. This is an inference, because the current state is ambiguous.
Different time phrases used along with perfect aspect may define (or imply) whether the action is ongoing or not. For example,
I have owned this car since 2011.
Clearly you still own it.
I have owned this car up to/until now.
Clearly you don't own it anymore.
It seems that with your original sentence, it’s the time phrase that conditions our view of the state of possession at the point of retirement.
Addendum: Concerning your idea about stative vs active verbs, I’m not sure if that’s relevant here. Look at the following examples.
By the time he retired, Alan had been married three times.
By the time he retired, Alan had gotten married three times.
Being married is a state, getting married is an action. But in neither case do we know if Alan is currently married.
You are saying "If I am given X, then I'll be ready to do Y." This is a conditional expression and you should follow the rules for that.
Note that your X can't be in past tense and your Y in future tense. If X has already occurred, then there is no uncertainty and the whole thing needs to be in the past tense to make sense.
If I had been given X, I would have been ready to do Y. (Expressing an uncertainty in the past which does not exist anymore by virtue of being able to say what happened. If the uncertainty exists in the present, X and Y must be present tense.)
If I am given X, I will be ready to do Y. (Expressing a present uncertainty and something that could/would/may happen upon a condition)
In present tense, Y can sometimes use the word would, i.e.
If I am given X, I would be ready to do Y.
is still all present tense. But will is never used to express anything in the past.
Best Answer
The key difference between the construction in:
1a "I will have received the money by then."
1b "I will be receiving the money tomorrow."
and the one in:
2a "I will have been given the money by then."
2b "I will be given the money tomorrow."
is not one of tense or aspect, but rather of voice. The latter pair of sentences use a construction in the passive voice.