I'm looking at buying a 2009 f150 xlt 4x4 with the 5.4 it has 260000km so I was wondering if there was anything to look out for

 

Cam phaser and timing issues. Take it for a good test drive and get it warmed up. Listen for a diesel sound at low rpm(under 1000) while under load. You could find a hill or just step on the brake. You will know it when you hear it if it has bad phasers or tensioners.
I haven't had any other problems. 74,000 miles on mine.