its going to be a LOT of work and time... and your not going to make much money
you need to find the parts
get them for as little money as possible
clean them up and make them something people will want to buy from you vs their local scrapyard
get shipping in order (proper packaging, insurance, etc)
set up a detailed web page that keeps track with your current inventory and lets your customer search for the parts they need and order them
it also has to let you know your current inventory
if you dont have something you need to go get it immediately
not to mention where are you going to store all of this inventory while waiting for it to move... stuff like body panels, seats, door trim, engines, etc all take up a LOT of space
and you dont want it clusterfucked all over the place... it will all need to be tagged and cataloged in a way that makes sense for ease of picking
is this going to be a one man show?
do you have other obligations that will require your time?
im not trying to shoot down your idea or flame it... its just that there are a lot of pieces to making this work... and running it successfully really is a bigger operation than you could feasibly pull off out of your garage
when you look at the time for finding the parts, getting the parts, cleaning the parts, inventorying the parts, putting them in their proper spot, getting the information and possibly images uploaded to the site, replying to emails and answering questions, replying to phone calls and answering questions, picking the parts, making appropriate changes to reflect this in inventory and on the site, packaging the items for shipping, scheduling pickup, notifying customer of tracking info, dealing with disgruntled customer who wants his money back because the part you sold him has some minor flaw that was not disclosed previously and he doesnt want your shitty parts, setting up return shipping, re-entering the item into inventory, eating the cost for that transaction, all while locating and getting more parts that need to be inventoried and taking orders that need to be shipped..... blah blah blah blah blah... when you factor in the time, money, and labor involved... you arent really going to make dick... hell it will most likely cost you money
you alone are not going to have the time to handle this on your own... doing this right would really require a decent sized salvage yard of your own and a staff of probably 8-15 people
you will need:
someone to answer the phones
a few wrenches to strip the parts off of the cars
a few people to clean parts then put them into inventory (same people can also pull parts when ordered)
someone to locate and purchase the salvaged cars your parts are coming from
someone to transport the salvaged vehicles to your location
someone to keep track of inventory
someone to manage and update your web site
if you already had an operational salvage yard and wanted to get it online, id say go for it... but you dont... and this is going to be way more trouble than it will ever be worth... there are easier and more enjoyable ways to die of a heart attack at a young age