Will I automatically get lifetime FREE updates if I buy an iPhone app? If I buy a paid iPhone app, will I be able to get free updates for the rest of the lifetime of that app or should I pay later for the updates? 

What's the norm? Can you perhaps give 1-2 examples?
Not entirely. The App Store doesn't allow for paid upgrades of the same application, say v1.0 to v1.1. But there is little to stop a developer from releasing the next version of an app as a separate purchase, v1.1 to v2.0.