Your lot should come with a mail box and a garbage can usually near the road.Did you delete it?
Check to make sure that your lot is a residential. You can see that from edit town, click on the lot and the ocon next to build/buy, use that to change it to residential.
If it already is.. I am not sure maybe someone else can help with that.
Build a garage just like you would a house, it just has garage doors. And if you want cars to store in your garage, put down parking spaces inside.
go to buy mode sort by function
ctrl+shift+c (hold all of them together) hit enter a menu bar will appear at the top of the screen type in testingcheatsenabled true (hit enter ) then ctrl+shift+c ( hit enter) type in buydeg on an ? will appear go to miscellaneous find a mail box there place it on your lot
then turn the cheats off in reverse
ctrl+shift+c in the menu bar type in buydebug off
ctrl+shift+c testingcheatsenabled false
after you do all that it is a good idea to save your game wtth the save as and then quit game then restart
