If there has been one objective that's been consistent throughout the Animal Crossing franchise, it's paying off your mortgage. It's the driving force behind a series without much drive, and for players who stick it out, they know paying down that mortgage means more room and more room means more stuff.
After you arrive at your island and find yourself the perfect spot for your tent, Tom Nook will present you with an itemized bill covering everything you're starting out with. As with every other bill you'll get in this game, there is no time limit on when you have to pay it off. However, given the size of the tent, many people will probably grow out of it right away.
Animal Crossing: New Horizons makes it easy to pay off this first loan with Nook Miles, the new currency that's earned through everyday island activities. The grand total of the bill is 49,800 bells or just 5,000 Nook Miles, and despite being given two totals for the different currencies, you can actually only use miles to pay this first loan off. If you want to get out of that tent and into a house ASAP, I've compiled a list of activities you can complete right away to earn enough miles.