Looking at a 97 f150 w/ engine knock

[craigt502]

Found a local selling a 1997 F150 Lariat eddie bauer edition.
Extended Cab 3rd door, short box
5.4L Automatic
Push button 4x4
170,xxx miles
Body is OK, no rust, some clearcoat peeling, etc.
$2500
The owner let me take it for the day/night to test drive it.
It runs and drives great, shifts are crisp, 4wd works awesome. Now the small problem.
When the engine is cold there is an audible knock coming from the engine. Sounds like a lifter tick but deeper. After the truck gets warmed up the knock is harder to hear. Is this something i should be really concerned about? Like i said other than hearing the knocking you wouldnt know its there. Going WOT is smooth and feels strong. Cant hear the knock above like 3000 rpms. Any input is appreciated thanks.