I wish you luck, but honestly, a 5 day base ticket that could get your friend into the four main parks, with no access to Blizzard Beach or Typhoon Lagoon or Pleasure Island and NO park-hopping, is $219.39 tax included. You might find some cheaper prices for tickets, but only for a couple of bucks, maybe 10 dollars cheaper. And you haven't yet included airfare (BTW, it'd be impossible to tell you how much airfare could be without knowing where you live. We don't need an address, just any airports close to you). If you have access to an airport that has Jetblue, they tend to have some of the most affordable air fares.
You might want to persuade your parents to call someone like Kingdom Konsultants (who post here) or the travel agents at AAA, who might be able to put together a comprehensive and afforable package price, where your friend could give your parents the 160 up front and maybe some more money every week until it's time to go. But even still, I wouldn't get your hopes up on getting park tickets AND airfare for 160. Your friend might need to raise some extra money somewhere. Sorry.