I'm going to tell you a few ways to get bells easily In WW.
Hoarding: When you find items store them in your house and sell them when you think you have enough.
Fishing: Buy a fishing pole from Tom Nook and catch fish. This can earn you bells quickly if catch big fish.
Bug Catching: This one is kind of hard because the bugs move fast and you can't move while swinging the net. If you catch a decent amount of bugs or a few rare bugs, you can make decent profit.
Trading: Trade with other people over wi-fi for expensive items/furniture. Some of them can be sold at a high price.
(there are other methods but these are the ones I know, hope this helps pay off your mortgage.)
Just ignore me. Just ignore me. Just ignore me. Just ignore me. Just ignore me. Don't look. Don't look. Please don't talk to me. Ignore me. Ignore me. Ignore me. Look away. Look away. Just look away. Stop staring. Stop staring. Stop staring...
Okay they're going away...
Don't turn around. Don't turn around. Don't turn around.