Select your Sim -> Open the Cell Phone Tab -> Select Move -> Select who moves and who gets kicked (kicking deletes the Sim from the game) -> Then select a house to move into. Understand however, how much available simoleons you have and therefore this may limit the houses that your sim(s) can move into.
Yes you can sell your house in the sims 3. All you have to do is select your Sim cell phone and click on it. This will give you the option of selling your house and moving to another one.
You are allowed to buy a vactation house in Egypt,china. and France but you need a high visa level
No you cannot buy a gun on The Sims 3.
No you can buy a prebuilt house or move in some houses from the inventory thing in edit town.
the mail box is always in front of a house or a lot when you buy one.