Question: How does their sister Megan afford all of her equipment?
Answer: She's just sneaky that's all.
Question: Why doesn't Helen like Josh?
Answer: Most likely because she finds him as a slacker at his job at The Premiere, even though she exaggerates with this.
Chosen answer: Well, she is the most liked sibling, so she can probably get more out of her parents, or get money from both of them without the other knowing, or as we saw in the Gary Grills episode she can get money from people easily by telling them all sorts of stuff.