A scrap yard owner usually buys older cars that are not workable or repairable, and then will strip them down to remove parts that are salvageable, reselling those parts alone. While auto parts at a scrap yard will have some wear and tear, as they're obviously not new, they are also often very workable and will still have lots of life left in them. If you're concerned about getting auto parts from a scrap yard versus buying them new, note a few times when this can be the best decision for you, or at least something acceptable and workable for your car repair needs.
Never compromise a car's safety, no matter the cost of parts; however, if the parts you need to replace won't affect the vehicle's safety, you might consider getting those parts from a scrap yard. For example, it's never good to use a second-hand bumper, as those bumpers absorb the impact of a crash, but you can often replace interior seats, trunk lids, front grilles, and other such parts with used pieces. Minor pieces like mirrors or dashboard vents can also typically be replaced with something from a scrap yard.
Longevity of your vehicle
Note your vehicle's overall condition and its expected longevity. If it has lots of rust or has very high mileage, it may not last for many more years, no matter the repairs you make. Investing in a new part may then mean that this part actually outlasts the vehicle itself! Buy used parts for very old vehicles so that you don't waste money on repairs for a car that you will eventually need to sell or turn over to the junkyard altogether.
If you appreciate high performance from your vehicle, or if you tow a heavy trailer or caravan, you may only want new parts that can withstand higher speeds and hold up under that added weight. However, if you're not overly concerned with the vehicle's pickup, don't often drive at very high speeds, and don't tow or carry anything particularly heavy in the vehicle, you may not need new parts. Older parts are durable enough for everyday driving, even if they aren't the best for holding up under excessive wear and tear. For commuting, running errands, and just your standard family sedan, you can use second-hand parts and have the vehicle function for your needs, without overspending on something that offers higher performance that you don't need.