I'm spitballing here so I could be wrong, but assuming a few things, one this is all being done by a single person (or the airbinb side and app side are being done by a single member LLC) if you took all the airbnb income and plugged it back into outgoing app dev costs shouldn't these two streams offset for tax purposes (ie 10k in from airbnb - 10k out for dev = 0 taxes)?

You'd then just be paying taxes on the income for the app sales.