"She sees that her trading is profitable, and her lamp does not go out at night." Proverbs 31:18 (NIV)
I'm focusing on this word profitable. The Bible says that "all hard works brings a profit" (Proverbs 14:23) and "the plans of the diligent lead to profit." (Proverbs 21:5)
While the above verses speak a lot about material gain, I think there's a spiritual application as well. For instance, I might work hard as a mother and homeschool teacher but not see any kind of material gain, such as MONEY. But I might see my children gain wisdom in the Lord, be smart and eventually gain good careers, and rise up to call me blessed.
Three verses in Isaiah chapter 44, verses 9, 10, 11, speak of profit in the negative. "All who make idols are nothing and the things they treasure are worthless. Those who would speak up for them are blind; they are ignorant, to their own shame. Who shapes a god and casts an idol, which can profit him nothing? He and his kind will be put to shame; craftsmen are nothing but men." (NIV)
Clear warning: profit, worldly or spiritual, comes only with hard work and God. Be certain you're worshipping the one true God because He's the only One who can give us profit that'll last.