Which of the following elements is part of a written mortgage?

A written mortgage is a legal document that serves as a contract between a borrower and a lender, detailing the terms under which the loan is secured by real property. One of the fundamental elements of this contract is the security interest in property. This signifies that the lender holds a legal claim to the property in the event that the borrower defaults on the loan. By including a security interest, the mortgage ensures that the lender has a means of recourse to recover the amount loaned, typically through foreclosure, if necessary.

In contrast, the other options listed are not integral parts of a written mortgage. A health insurance policy pertains to health coverage and is unrelated to real estate transactions. A job offer letter is associated with employment and income verification but does not connect to the terms of a mortgage. Lastly, a rental agreement involves the lease of property rather than the financing of it, making it irrelevant to the composition of a mortgage document. Thus, the inclusion of a security interest in property is the essential characteristic that defines a written mortgage.