Mortgage, a noun or a verb?

Hi,
My name is Kelvin
Yesterday i was attending TOEFL Preparation class in my college when the lecturer asking me to make a sentence that contains causative, relative clause and models.
Then i made one sentence using 'mortgage' as a verb, but my lecturer said that was wrong. But i still feel like I'm correct.
So, can anyone can help me regarding this matter?
I need a clarification about this subject, Thank you very much and sorry if there are any mistakes in my writing above because I am still learning. ^^

Thanks again,
From Indonesia