Can I buy a product and use it to make something else and then sell it?

No, if you legally bought the item, you are free to re-sell it as part of another item. Whether the final product creates other issues, such as copyright or patent infringement, is still possible.

That is legal to do unless you are removing parts required by law for safety or necessary to meet EPA regulations. IE you can't buy a car and remove the catalytic converter and sell it. Also you can't buy a book and then use the general plot line or the characters to make another book. This would violate copyright law and be considered a derivative work. If you buy a book the photos in it can't be reproduced and sold or put on a website as you have the rights to own the book not to the individual images. This is a very short answer to a long question but i think you can get the gist of it.