it could be a bad motor mount and your fan is hitting the fan shroud when you press on the gas have someone look under the hood at the fan put it in drive and hold the breaks and give it some gas.
possably a leak in the vacumum hose going to the brake booster. i'd spray startind fluid around the vac. hose til i heard to engine idle up. then the leak is in that erea.
That is the metal of your exhaust system, most likely a heat shield contracting as it cools. As the metal heats up it expands and as it cools it contracts or becomes smaller so the sound you hear is the metal moving as it does this.
it is uncountable because many people can buy a car and the will be using it for just once in a week (the answer is yes. car of eight years is still on the road
I assume (grrrr) that it's in both your names, yes you can take it, but they have every right to take it back, because it's half theirs.