Nissan Altima: Some noise in Engine but none when clutch is applied

I am planning on buying a 1994 Nissan Altima SE. It has some noise in the
engine. But When clutch is applied and engine raised there is no noise.
Can anybody help me.

Also Does it have a timing belt. Would it need change if the mileage is
112K

Thanks

The sound is like a motor running. I hear it obvious when in 1 and 2 gears.
Maybe since the noise of the traffic is more or the disturbance is so much
that I do not hear that loud when in 4th or 5th gear.

The sound DOES NOT increase with speed or gears. The sound as I said is
like a constant motor sound