I have heard that an actual scrap yard is a low margin business. If you invest 40K that means some of this will go for equipment, land, etc...
The balance will go for actual inventory. How often can you turn what is left into a profit? How much profit do you have to make (this is margin plus turns) also called cash flow requirement.
This is the type of thinking that you need to achieve before you ask anyone for a business plan. Otherwise you could have a great plan but still not understand what it means.