With “have” the sentence suggests that the speaker still hasn’t achieved the goal of becoming an entrepeneur. Without "have’ one doesn’t know if the goal has been achieved, but if I am forced to choose I will say that the goal has already been achieved.
“had wanted” also suggests that the goal has been achieved, or possibly abandoned.
If the person already is an entrepeneur, I would definitely use simple past tense.
My reaction to the two sentences is basically the same as Canadian45’s:
If I heard someone use your original sentence, I’d probably assume that the person already IS an entrepreneur. However, if that were the case, I also think it would have been better to say “From the moment I entered the work force…”
If the present perfect were used in the sentence, I’d tend to assume that the speaker is not an entrepreneur yet, but wants to be.
I think the crucial point is that the verb ‘want’ by its very meaning indicates a period of continuing duration. By making the tense Present perfect you are simply emphasising that the ‘wanting’ has been going on for some time. As for the difference in meaning I would suggest: Since the moment … I wanted to be an entrepreneur indicates: And as you know I became one in the end. Or: Since the moment… I have wanted to be an entrepreneur indicates: And as you know this has now happened and now I am one.
I’m sure since 2006 English grammar has even further been murdered with the overuse of everyday bad grammar. I had to register just to add my two bits, because even native English speakers often kill the perfect tense and don’t have a clue as to how to use it correctly. “Since the moment I entered the work force, I have wanted to be an entrepreneur,” is correct use of the present perfect. The idea/ambition began in the past, and conitnues into the present; in this case, the achievement of working as an entrepreneur. “Since the moment I entered the work force, I had wanted to be an entrepreneur,” is correct use of the past perfect tense, and emphasizes that the desire/ambition has been realized/achieved/completed. The difficulty in understanding the perfect tense and all the nuanced ways to apply it, is due to the flexibility of the aspect of an action/or idea being completed at anytime up to the point of completion, to the present time.