Well Pastor Levi, I know I am just a woman, but I've been crunching some numbers to make sure you know where to start the bidding. Luckily, the Bible lays out a proper price range for us.
"And thy estimation shall be of the male from twenty years old even unto sixty years old, even thy estimation shall be fifty shekels of silver, after the shekel of the sanctuary. And if it be a female, then thy estimation shall be thirty shekels. And if it be from five years old even unto twenty years old, then thy estimation shall be of the male twenty shekels, and for the female ten shekels. And if it be from a month old even unto five years old, then thy estimation shall be of the male five shekels of silver, and for the female thy estimation shall be three shekels of silver. And if it be from sixty years old and above; if it be a male, then thy estimation shall be fifteen shekels, and for the female ten shekels." Leviticus 27:3-7
Now, according to
this wickedpedia article, silver shekels ranged from between 9 and 17 grams, and according to
this site, the current price of silver is $764.09 per kilogram. This means your daughter is worth somewhere between $68.77 and $129.90 (I rounded up, of course). Now, I believe that the price of silver is expected to rise, but lets say it stays the same. If you keep your daughter for seven years, you could triple your earnings.
EDIT: I forgot to take into account the shekel of sanctuary. Feel free to add between $6.88 and $12.99 to your asking price.