Front End Knocking Noise

Trying to buy more time with our van and trying to see if it is worth dumping money into. Good portion of the time (75%) the front end is creating a knocking noise. Noise is produced when engine is cold, warm or hot. Here are the times it makes the noise:

1) When starting from a braked stop and accelerating it will start knocking only on the first half of first gear. If it is not making the noise while accelerating straight I can often recreate by turning the steering wheel slightly left or right and it will create the same knocking noise, but once the rpms/speed get high enough it quits about half way to 2nd gear.

2) Same pitched noise occasionally when idling at stop - braked or when gear in park. Goes away once accelerating. If knocking when idling will almost always make knocking noise when accelerating, but idling noise isn't always necessary to get above #1 noise.

3) Oil level low light comes on and off randomly with or without knocking noise. Oil is not low on dipstick, but maybe we're measuring low pressure?

We hear the noise inside the van and if we stand outside while car is in park we cannot hear it over the engine.

So...I am not a mechanic and do not even know where to start looking. The noise goes away once car accelerates a little. It's almost like when there is torque on the engine the noise is created in acceleration, but what about when it's idling? Idling creates more of a random knocking noise and when accelerating more of an increasing grinding/knocking up until we are up and moving over 10 mph or so.

Can anyone give suggestions of where to start looking for problems?

Motor mounts, exhaust sytem, catalytic converter, sway bar mounts, CV joints/half shafts?