First get yourself a chunk of land. It doesn't have to be a large chunk, just a few acres will be fine to begin. Then you will need to make sure that the land is zoned or can be re-zoned for your business. After you got that covered & have the appropriate business licenses. you will need a tow truck, forklift, basic hand tools, & a cutting torch. Let's not forget the privacy fence also! Thanks to Tipper Gore thinking that salvage yards are a eye sore, we now have to build privacy fences around them just so her pretty little eyes don't get hurt!
Now that you have everything.... Start advertising to haul off junk & wrecked cars and trucks. You'll see a lot of people advertising to pay cash for those. Some pay $25, Some pay $50, & I've even seen people pay $75 & $100 for a junk car. Drag it back to your yard & begin dismantling it. After you have a good collection of cars & parts... Advertise your salvage yard & your in business.