Truck purs like a cat when turning on. Engine Light comes on, blinks, then stays on. Is there a typical problem associated with these issues?

Apparently the three main problems with it is the codes were wiped so it
took a while of driving before it came on, needs new ball joints, and there's
a misfire in the engine, if you give it some gas then lay off it, the RPM
needle will dip to 500 then back up to 600 and bounce a few times before
settling at 600. Got this from a lot, said they would take it back or repair it if
it has any major mechanical issues, this thing won't even start so I'll have to
get it towed down the street to get it looked at again and see exactly what
the problem is.