You can edit occupied homes. You don't need a mod to do this, you only need be in edit town mode and evict the household. Pay close attention to how much money the evicted family has because they will need to re-purchase their home in order to place them back in the world.
Once the household is on the clipboard (on your screen), their home will show as unoccupied, note the cost of the home.
Simple math will tell you how much money that household has to spend, just deduct the cost of the home from the amount shown on the family's screen. The remainder is how much cash the household has in its 'family funds'. Don't spend over that amount or else they won't be able to afford their home at the end of this.
Select their home and use the buy/build icon. This will take you into their home so you can make changes. You can buy or sell their stuff. If you are buying things, be certain the family can afford the things you are adding. If a washer costs 1,500 make certain the household has that amount in their family funds.
After you finish making changes, return to edit town mode, click on the household, select the 'Place' button and re-select their home. The game will move them back in.
Easy :)!