Pros:

They go to the same school, which would make seeing each other a lot easier. 

Josiah would be hooked by Phoebe's vibrant personality - he loves people who can keep up a conversation. 

He's very curious, and she'd offer him fodder for infinite questions, which Josiah would be happy about. 

Cons:

Phoebe not believing in love would upset Josiah, because that's one of the few things he really does believe in. He also believes that everyone is deserving of love, which probably wouldn't bode well with Phoebe. 

Josiah is a fairly emotive, confident person and would have a hard time understanding Phoebe if she were secretive or hiding her real feelings.