Which of the following best describes an "assumable mortgage"?

An assumable mortgage is best described as a type of financing arrangement where a buyer is able to take over the seller's existing mortgage and continue making payments under the same terms specified in the original loan agreement. This can be advantageous for buyers, particularly if the existing loan has a lower interest rate than current market rates, allowing them to benefit from potentially lower monthly payments without having to secure a new loan.

In this context, the other options do not align with the definition of an assumable mortgage. A mortgage with adjustable interest rates over time pertains to loans that can fluctuate based on market conditions, which does not relate to taking over an existing mortgage. A new loan processed through a third-party lender refers to obtaining a completely new mortgage rather than assuming an existing one. Lastly, a mortgage that only applies to first-time homebuyers restricts the definition to a specific demographic and does not encompass the concept of assuming someone's existing mortgage obligations.