[grueful]

Make up a number. Double it ASAP. Then double it again.

Then move to daily billing, or project-based billing if you have a lot of high-similarity work with relatively time-definite scoping. Either way, not hourly.

For a developer, floor should be like $50 if you are REALLY new, and totally lack confidence to pitch any other way. Then with the doubling after you have some success to bolster your confidence.

Typical rates for iOS are north of $100, often well north (think multiples). Really, really north if you use project-based billing and leverage a domain specialization.