Like the title says, I'm creating an app that's based on users buying virtual currency that can be spent on other users (if other users answer their questions), like a paid information exchange marketplace.
The person who answers can then "cash out" their virtual currency for real money (funds transfer).
Can I use IAP for this specific case?
If you want to pay User B based on chits purchased by User A, that step is all outside the app and on you to make happen.
Your problem is that IAP cannot be used to purchase real world goods. In your case it's not 'to purchase' but rather 'to redeem'. So that does not violate the guidelines - but Apple would need to trust that all you are doing is 'redeeming' and not providing some real world item in exchange for the IAP currency.
But you have another problem (and I have the solution). You need to protect against a user purchasing the currency, creating a backup with the currency recorded, transferring the currency and then restoring from back-up. (And repeating over and over again.) To prevent that you need a permanent memory to record the transfer of currency into or out of their 'account'. You can do that with your server or with the public database in CloudKit.
