Purchase of a Business » used between the Seller of business and a potential Buyer of a business. Eventually, you would use a Business Purchase Agreement to complete the deal. Purchase of Real Estate » used between the Seller of real property and a potential Buyer of the real property. You would use a Real Estate Purchase Agreement to complete the deal. Purchase of General Property » used between the Seller of personal property, such as a car or jewelry, and a potential Buyer of the personal property. You would use a Personal Property Purchase Agreement to complete the deal. Other Transaction » used between parties to document a potential transaction, such as providing goods or services over a given period of time.
Without job-level specifics, it can be tempting to get stuck in an "I'm awesome" loop without giving enough specifics. If you have a general idea of what job groove you'd be seeking at this particular company, build your letter body around that. If you're truly just trying to get a foot in the door at a company, you can use clues from your research about the company. What does their website say about their mission and priorities? What do current and past employees say about the company in online chatter? Even without specifics, you can cobble together a pretty good idea of what the company is seeking in potential employees. Sell your skills and experience points that are special to you, and especially relevant to your industry.