Ask HN: iOS app using WP as back end. Doable?

I have a small niche marketplace online business , its one man shop. It's running on WP. I want to build an iOS native app(SWIFT) while still using a WP Backend. I can't afford a custom backend. I have a buddy who is a SWIFT dev with a day gig, he will give me a reduced rate. Im comfortable with WP. To avoid the 30% apple fee. I want to charge customer for their product listing inside the APP in WEB via email after they upload images + summary of product listing (pending approval) I get a notification ( via email) of new Listing and email customer a STRIPE payment link, they pay and THEN I make the listing live in the APP. I would LOVE some feedback from the community on if something like this doable , someone who has used WP as CMS for an iOS app and charged in WEB. Thank you.