This question is not about marrying two sisters!
Here's a short recall of events on Yaakov's marriage with Rachel and Lea:
- Yaakov comes to Lavan knowing he should marry both Rachel (already agreed between the families, Rashi) AND Leah - Eisav's "fiancee", as Yaakov took all Eisav's blessings. (No need to discuss it here, it is only an assumption, it does not relate to the question).
- Yaakov meets Rachel and "falls in love".
- Yaakov offers Lavan to work 7 years (to pay) for Rachel.
- Yaakov finishes working 7 years and demands Lavan to bring his wife to fulfill the Mitzvah of Pru uRvu (to establish the 12 Tribes).
"Give me my wife, **for my days are filled**, that I may go in unto her"(Ber 29,21)
- Lavan throws a feast and disguises Leah as Rachel.
- Yaakov sleeps with Leah.
- Yaakov demands to have Rachel and Lavan offers him to wait one week to have Rachel also.
- Lavan gives Rachel to Yaakov.
- Yaakov works 7 additional years.
According to Jewish Halakha this order rises legitimate questions:
- According to Seder Olam, Rachel and Leah were grown up (21yo) and did not need their fathers agreement and power to marry as underaged girls. Yaakov could marry them both on the spot with two witnesses only by dancing before them or by writing a Shtar. No money needed. He was also old and pressed to establish the tribes, so in fact he could do it 7 years earlier.
- If we assume that the wage of the 7 years Yaakov worked were meant for Rachel's Kiddushin for Lavan, she was his rightful wife on the last day's sundown as he demanded from Lavan to bring his wife not fiancee. So Rachel was already his wife before the wedding night.
- Leah was not Mekudeshet in any way in the whole story, not bought and not even by Bieh, as none explicitly meant it. It was seemingly a mere Beilas Znus.
- There was no need to ask Lavan's permission again to have Rachel as explained above.
- What were the additional 7 years of work for?