with this mod you can buy stolen cars and guns much cheaper that the ones in the game because it is stolen, it help a lot if you are at the beginning of the game or if you are too stingy to buy weapons at ammo-nation , just go to the green bottles bar, you will walk up to the old man sitting in one of those tables after a short dialog (if you see the dialog once and save the game you don't have to see it again) you will be able to buy the item just pressing the key E next to the old man and a menu will be opened, you can buy tec9, ak47, sawnoff shotgun, blade and a euros if you don't have the money you won't be able to buy and the old man will say something like "No money no goods" and if you kill the old man and save the game you won't be able to buy the itens anymore unless you delete your cleo_saves folder
for install just paste cleo folder into your gta sa directory you will need cleo 4 library