Lorenzo is pals with Antonio and Bassanio. More important, however, he's the guy who hits the jackpot when he elopes with Jessica. Remember how Jessica loaded herself up with her dad's ducats and family heirlooms when she ran off to get hitched behind Shylock's back? Well, all of that money becomes Lorenzo's the second he weds Jessica.
Now we're not necessarily saying that Lorenzo is a gold digger like Bassanio. We're just saying that Lorenzo is a really lucky guy.
Unlike Bassanio (who talks about Portia like she's a cash cow), when Lorenzo talks about Jessica, he says he loves her because she's smart, beautiful, and loyal:
Beshrew me but I love her heartily;
For she is wise, if I can judge of her,
And fair she is, if that mine eyes be true,
And true she is, as she hath proved herself,
And therefore, like herself, wise, fair and true,
Shall she be placed in my constant soul. (2.6.6)
At the same time, we should also point out that Bassanio makes this declaration of love right after Jessica promises to "gild [her]self / with some more ducats." We also notice in this passage that Lorenzo says "beshrew me [evil befall me] but I love her heartily." Clearly Lorenzo has at least some anxiety about marrying the daughter of a "faithless Jew" (2.4.7).
This raises an important question: In a play that's chock full of anti-Semitic characters, are we supposed to read Lorenzo's willingness to marry Jessica as a signal of his progressive, open-minded attitude about race and religion? What do you think?