Several loans are repaid throughout the course of the game. These are tasked to the player by Tom Nook in Resident Services, which is situated in the town centre. These loans include:
5,000 Nook Miles to repay your tent, NookPhone, etc;
98,000 Bells to pay for the default house upgrade;
[insert other house upgrades here]
There are also a bill set by Timmy to gather some items for him to upgrade the shop. These include;
30 Softwood
30 Wood
30 Hardwood
30 Iron Nuggets