In some ways, I'd recommend restructuring the app a little bit and start low-level and allow the user to do his own research and build up his info. For example

In some ways, I'd recommend restructuring the app a little bit and start low-level and allow the user to do his own research and build up his info. For example, let the user put it the price of a house. That's it. With 0% down payment. Show them the graphs and the monthly payment (without taxes/insurance). In 1 second, they immediately have something in front of them. Then, let them enter in a down payment, as they are doing so in real-time update the graphs/payments. Then they choose 15 or 30 year, and keep adjusting parameters. They started simple but are slowly building up to see what makes a difference and aligning it with what they can afford. At least, that's how I approached it. I want to see graphs/payment before I even have to tell you my savings.