I am planning to start used car parts business

You don't have a "plan" you have an idea.

Selling used car parts is fraught with potential problems, especially for someone on the other side of the planet.

Most "shade tree" mechanics have known go-to sources.

First off what do you mean country side ? A person living in the country fixing their car or something else.

Retired people usually don't want to fool around with their own cars. They either made enough money to take it easy and enjoy life. Or they suffered something that will keep them from being able to physically work on a vehicle. Usually any other car tinkers will have their own source of parts as noted in another post.

Junk people ? You mean the people are Junk or something else ? You are in over your head. Most reputable yards have their own websites and ship through there. They maybe toying with you. If you think you can bring them sales.

Another thing, people that need used parts will often go to a local salvage yard to pick the part up before starting the job. This way they can match up the part to make sure it is the right one. Nothing wastes time more than ending up with the wrong part from the start. Or worse yet getting a used part and finding it either broken like a cracked lens or ordering one model part and getting a different year or one that is for another model.

FYI - about used parts issues on a current model year mirror. Is the used mirror manual, power, heated, does it have a puddle light, does it let have a signal built in it, or does it fold in automatically after the vehicle is turned off.

Ok so I have a list of all the USA based phone numbers... do you think you are going to start at the beginning of the list and call everyone and say "Hi, my name is Bob. Do you have a car in need of repair? Do you need car parts?" It simply does not make sense.

Honestly you need to be looking at eBay as an option. list a part, Sell a part, keep your commission, and then pay for the part to be sent from your parts provider to the customer.

I would call eBay and ask specifically about the rules in becoming a Drop Ship Merchant.

To generate leads you may contact with any lead generation expert who will do it for you. Also you can contact with an e-commerce expert before you proceed in your business, thanks!

You will run into Alot of returns and charge backs selling junkyard parts online. Not worth the effort a better move would be to sell new quality parts.