Run the numbers before the emotions, because giving up a very low fixed rate is expensive and easy to underestimate. Do a direct comparison: - Moving: the total all-in monthly payment on the larger home at today's rate, plus the one-time hit. Selling typically runs 4% to 6% of the sale price in costs you don't get back, on top of the buying costs on the next place. - Staying: your current low-rate mortgage plus the payment on a HELOC or second mortgage that funds an addition. A HELOC typically carries a variable rate, so stress-test that payment before you commit. The math often favors staying when your floor plan and lot can genuinely accommodate a sensible addition. Keeping the low fixed first mortgage and borrowing only for the expansion usually beats trading your whole balance up to a much higher rate. Moving may be unavoidable when the layout or lot simply can't fit the space you need. No amount of rate loyalty fixes a lot that's too small, and buying becomes the realistic path despite the rate sacrifice. One more factor in a state like California: staying and building can preserve your lower retained property-tax basis, while buying a larger, pricier home can trigger a meaningful property-tax jump. Confirm that piece with a tax professional for your situation. If it helps to see both scenarios side by side with real numbers, that's a good free Roadmap conversation.