There is no clean formula, but the direction never changes: a new car payment shrinks how much home you qualify for. As a rough illustration, financing $50,000 on a car can easily create something like a $1,000 monthly payment, and a payment that size can cut buying power by roughly $150,000. Treat those numbers as illustrative, since the exact figure moves with rates and with where your ratios already sit. How much you actually lose depends on whether you were maxed on your housing ratio alone or also carrying other debt that loads up the back-end ratio. The simplest fix is the one our viewers call out in the chat every time, and they are right: buy the car after you close on the house. Nothing about the car changes if you wait a few weeks. Everything about your mortgage qualification can. If a car purchase genuinely cannot wait until after closing, call us before you sign so we can tell you what payment your file can absorb without breaking the approval. It takes a few minutes and saves a lot of heartburn.