This politely worded resignation letter cites low pay as the reason for the employee departing.
January 25, 2018
Dear (Employer Name),
I am sorry to announce that I will be resigning from (position), effective (date). I will miss this place and this team tremendously, as I have learned so much about (field) and felt like I've been doing important and meaningful work. However, with (new baby/new house/school), I need to seek out employment that will help me stave off debt. I appreciate your understanding, and I wish you all the best in the future.