1994 Ford Tempo loud rattling noise

1994 Ford Tempo mileage: 77,000. Dear Bob and Ken, our car was just running fine. Then one day last week, it started having a rattling noise. When the car is in idle it's loud, when we step on the brake, it's loud. The only time the sound decreases a bit is when we put it in park. Like when at a red light it's noisy so we put it in park and it's not so embarrassing. My husband first thought that maybe it was the water pump or something. Then someone said it might be the timing belt/chain going out. How can we tell for sure if it’s the timing chain? We bought the car last year from used car lot. Last March made one year we owned it. We can't afford another car and we still have three more years loan on it. Please help. My husband can replace a car part, but timing chain, that's a bit much for him. Please answer back. I appreciate it. Thank you Geraldine