K would likely live a relatively normal life - in the same way as real-life people do when they don't have fingerprints (such as military vets who have lost both hands).
The issue of K's confusion regarding having no fingerprints would likely be resolved by J, who would follow standard MIB protocol by providing a fictional explanation of events to K immediately after the memory wipe. This seems to be a reliable method of containment for memory wipes, and my guess is that it applies to K just as well.
Additionally, I would guess that the MIB probably provide some degree of anonymous help to their former members' legal bureaucracy hassles - even if only for the sake of further containment.