Buy mode

Buy mode is one of three independent modes in the game (the others being Live mode and Build mode) that appears in The Sims, The Sims 2, The Sims 3, and several spin-off games. It can be activated by clicking on the Buy mode icon in the user interface, or by pressing. Buy mode allows players to purchase items from an object catalog and place them on the current lot, sell objects that are on the current lot, and arrange objects on the current lot. Construction-related elements such as doors, windows, fences, and stairs are not associated with buy mode, but are in build mode. Buy mode largely focuses on furniture and appliances.

The descriptions of many of the objects available for purchase in the game (particularly the less expensive ones) involve humor, sarcasm, insults towards the player, and wit, and serves as comic relief in the game. For example, one of the cheapest cars available in The Sims 3, the "Big Lemon", notes that although the car's doors are jammed and its ignition is faulty, it is still worth buying. Another example is the outdoor entertainment item "Foot-and-Hand Ball" used to train the athletic skill, which references and pokes fun at American football, which, despite its name, rarely involves contact with the ball via the feet.

Mechanics
The game is paused while the player is in buy mode. Game time only passes when the player is in live mode.

Many of the tools available to the player, such as the hand tool, eyedropper tool, and design tool, are also available in build mode and will function just as well on items placed in build mode, like fences and trees, as they will on items placed in buy mode.

In some situations, buy mode, as well as build mode, may become disabled, such as during a fire, burglary, or other major event. This is done to prevent modifications to the lot that may impact or prevent a game event from occurring. After the event has ended, build and buy modes are re-activated. However, buy mode as well as build mode can be activated through the  cheat. In general, buy mode and build mode are also disabled when a Sim is on a community lot. In The Sims 3, however, clicking the Build or Buy buttons while on a community lot will bring the camera back to the home lot of the Sim, and open Build or Buy mode there.

In The Sims 3 players can access blueprint mode from build or buy modes, which allows them to plop down pre-designed rooms to form a floor plan.

By function categories
The Sims and The Sims 2 automatically sorts the buy mode by object function—clicking on the buy mode icon will reorder objects to sort by room. Prior to Hot Date, the function sort did not have sub-categories. Unlike some features introduced in Hot Date, this was carried over into The Sims Deluxe Edition. In The Sims Castaway Stories buy mode is renamed to "barter mode" and its objects are only categorized by function.

By room categories
Buy mode in The Sims 3 is automatically sorted by room, but selecting the "Sort By Function" icon will resort the buy mode by function. The items within each category are sorted by function, with some items included in multiple categories.

Buy mode tools
Hand Tool (hotkey H): Used to pick up, rotate, and move items. Some items cannot be moved, while others can only be placed in certain locations. When holding an item, the highlighted tile(s) which show its footprint also show which side is considered the front (depending on the object, this may or may not be the side Sims will approach it from). If the tile is highlighted green, the item may be placed at that location; otherwise, it will be red—attempting to place the item will give a description of the problem. Objects can be picked up by clicking on them. When holding an existing object, the player can delete the object by clicking on the bottom of the screen, or by pressing the key. To rotate an object, the player can either use the and  keys, or drag the cursor around in the direction they wish their object to face in. In The Sims, the direction the object is facing in is indicated by the arrows shown while rotating an object with the mouse—the white arrow indicates the front side of the object, while the black arrow indicates the back.

Eyedropper Tool (hotkey E): When pointed at a wall covering, floor covering, or most objects, will show the name of what it's pointed at. Clicking on a wall or floor covering will switch to the appropriate area of build or buy mode and select that covering so it can be applied. Clicking on an object will make an exact duplicate of it, and will focus the catalog on that object. The player can also duplicate an object with the hand tool after grabbing and placing it down while holding down the key.

Design Tool (hotkey R): Allows a recolor change for a selected item. Costs §15 per use, regardless of what was changed. Objects that do not have recolors cannot be changed with this tool.

Create a Style (hotkey R): This tool opens up the Create a Style menu, which allows the player to redecorate and recolor most items using both preselected styles and colors, or by manually using a color wheel and different available textures. Use of this tool is free.

Top-down View (hotkey T): Switches the display to (or from) a view from above.

Undo/Redo (hotkey combination CTRL + Z / CTRL + Y): Allows the player to quickly undo or redo an action. The undo/redo history will be kept even if the player switches between buy and build modes. In The Sims, this was only available in build mode, and the history did not carry over into buy mode..

Sledgehammer Tool (hotkey J or K): First introduced in The Sims 2: Pets and carried forward into later games, the sledgehammer tool allows players to easily remove walls and objects. The tool can be used on individual objects and tiles, or by clicking and dragging around an area to remove multiple objects.

45 degree angle (hotkey G: Switches the display to (or from) a 45 degree angle view from the floor, which allows the player to see the ceiling more easily.

Family Inventory
The family inventory is a space where large objects (too large to be held in a Sim's personal inventory) are kept. Certain opportunities may make an object available in the Family Inventory. When a Sim family moves, if "pack furniture" is selected, all objects in the household will be placed in the Family inventory, to be moved and rearranged in the new house.

Buy mode in other games
Buy mode is referred to as "barter mode" in The Sims Castaway Stories, and "furnish mode" in The Sims Medieval. Despite the different names, the function of these modes is similar to the traditional buy mode.

In The Sims 4, buy mode is not an independent mode, but is instead fully incorporated into build mode. Build mode in The Sims 4 contains an object catalog (including object sorting by room and function) and a family inventory.