The latest articles on DEV Community by Jenny Tate (@jennytate). https://dev.to/jennytate https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4182340%2F3fcd3d8c-1d8c-49df-b9ea-2e09fec6f571.jpg https://dev.to/jennytate en Jenny Tate Tue, 13 Oct 2026 13:44:58 +0000 https://dev.to/jennytate/i-gave-chatgpt-a-real-mortgage-calculator-36kb https://dev.to/jennytate/i-gave-chatgpt-a-real-mortgage-calculator-36kb <p>Ask an AI assistant to compare two mortgage offers and you'll get a fast, confident answer. The catch is that a chatbot predicts words. It can sound sure and still get the arithmetic wrong, and with a mortgage a small slip is thousands of dollars.</p> <p>So I did something about it. I'm Jenny Tate, a <a href="https://jenny.mortgage/" rel="noopener noreferrer">Burlington mortgage agent</a>, and I've published Mortgage Tools by Jenny: six Canadian mortgage calculators that plug straight into an AI assistant like ChatGPT. You chat the way you normally would. When it's time for the math, the assistant hands your figures to my tools, and the answer comes back as a clean card right in the conversation, with every number calculated instead of guessed.</p> <h2> What that looks like </h2> <p>Say your renewal letter is on the kitchen table and another lender has sent you a quote. You type something like "Compare these two offers over five years" and give it the figures.</p> <p>Here's an example with made-up numbers (this is not a mortgage on offer). The balance is $450,000 with a 25-year amortization and a five-year term. "Current lender" comes to $2,589.12 a month. "Switch lender" has a slightly lower rate, $2,538.38 a month, a $350 appraisal fee and $1,500 cashback.</p> <p>Most of us would look at the $50 difference in the payment and stop there. The tool keeps going. Over 60 months it showed a modelled borrowing cost of $102,938.74 for staying and $97,469.13 for switching. That is $5,469.61 lower on those figures. It also showed what you would still owe at the end: $397,591.54 against $396,316.33.</p> <p>Then you keep talking. "What if the appraisal is $800?" "What if I only look at three years?" Change one thing and the whole picture updates. That's the part I like most. It feels like a conversation, and the math underneath is done by a calculator.</p> <h2> Six tools, one chat </h2> <ul> <li>Compare two or three renewal offers</li> <li>See what extra payments do to your mortgage</li> <li>Weigh breaking your mortgage early against staying put</li> <li>Look at rolling other debts into your mortgage</li> <li>Find out which figures you're still missing</li> <li>Get short preparation guides written for Ontario</li> </ul> <p>The tools only use the numbers you give them. If you don't know a cost yet, it is never quietly treated as zero.</p> <h2> The honest part </h2> <p>These are educational scenarios, not advice, an approval or a lender quote. The tools don't predict rates, calculate your penalty or pick a lender for you. Your lender's documents decide the real numbers. The calculators work anywhere in Canada, and my own mortgage services are in Ontario only.</p> <h2> Try it on your own renewal </h2> <p>You add the tools once to your assistant as a custom connector by pasting in one address. No sign-in, no account, no email. Whether you can add a connector depends on your assistant and your plan. Type in mortgage figures only, and leave out your name, address and banking details.</p> <p>The steps are on the <a href="https://jenny.mortgage/mortgage-tools/" rel="noopener noreferrer">Mortgage Tools by Jenny</a> page. Grab your renewal letter, grab the other quote, and see what the numbers say before you sign.</p> <p>Jenny Tate, Mortgage Agent Level 1, FSRA licence M22002086. Tango Financial FSRA 13691.</p> ai chatgpt finance