Cheap auto parts? How cheap is too cheap? Don't waste your money on poor quality parts; I've learned from experience. Sometimes they might get you by for awhile, but why spend a few dollars less for something that might last only a month or a year and leave you stranded somewhere? Then you get to buy it again; now you've paid twice as much for something that lasted much less than a quality part. (You know what I mean, don't you?)
What should you look for? Quality that is affordable, from a reputable supplier with a good reputation, and a good guarantee.
Should you buy new, used, or rebuilt? Should you buy locally or online? The same rules still apply. Common parts like starters, alternators, and water pumps, can be rebuilt and last a long time for less money than new ones. Sometimes junkyard parts come with a guarantee (of sorts) and a low price that makes them worthwhile, as long as you realize they were "used" by somebody, and are already partly worn-out. You get what you pay for -- sometimes -- and sometimes not. What's the suppliers reputation? What's the guarantee? Will they give it to you in writing, with a receipt?
When I was a teenager (in the 60's,) I used to dream of someday having my own car. I found an old copy of a popular automotive catalog with little black & white pictures, and wore it out looking at all the cool parts I would buy someday. Well, a few years later, my dream came true. I found a 1959 MG, black with red leather interior and wire wheels; very good condition, for only $600! I borrowed some money from my dad, and drove it home.
Still had the old catalog, and ordered a couple things to "fix her up". Good quality at a price I could afford. (That's what I liked.) Then once, I got a part that was supposed to fit all cars (but not MG's, I guess), and they quickly refunded my money. (That's what I mean.) Now even today, I still trust them for supplying quality parts at reasonable prices. (That's what I appreciate.) I still order from them for my 'Vette, my truck, and motorhome.
Today, there are thousands of companies selling millions of auto parts. Some expensive, some cheap, and some "good quality at reasonable prices". I believe in supporting your local auto parts stores, and the same rules still apply. But sometimes, it's fun to look at all the great online catalogs. If you choose to order online, you can't inspect every part you order, and you can't take it apart to see how it's made. This is when you have to rely on the reputation of the supplier, their promise of good quality, and their "no-hassle" refund policy if you're not satisfied for any reason.