Did you read the part on the website about how they came about to have such a large family? I'll copy & paste it here:
"Jim Bob & Michelle Duggar married July 21st, 1984. At that time, they chose to use the birth control pill. They thought, “We don’t want children right now. We can’t afford them. We want children in our timing, when we’re ready.” Four years later they decided to have their first child. Then, Michelle went back on the pill, but she conceived and had a miscarriage. At that point they talked with a Christian medical doctor and read the fine print in the contraceptives package. They found that while taking the pill you can get pregnant and then miscarry. They were grieved! They were Christians! They were pro-life! They realized that their selfish actions had taken the life of their child. They prayed and asked God to forgive them, and to teach them to love children like He loves children. They asked God to bless them with as many children as He saw fit in His timing. Right after that Michelle got pregnant with twins! To date they have been blessed with 16 children, (10 boys and 6 girls) Joshua, Jana & John-David (twins), Jill, Jessa, Jinger, Joseph, Josiah, Joy-Anna, Jedidiah & Jeremiah (twins), Jason, James, Justin, Jackson, Johannah (& Jennifer due July 28, 2007)"
"What does Mr. Duggar do for a living? He needs to have a big fat income to provide for that many kids." (sorry, I don't know how to 'quote' that?!)
He and his wife are real estate agents.... :\ Better 3 is plenty for me, lol