When you're at your property,you could probably sell some of your food or drugs (which you could disguise as some other objects),or maybe sell your weapons and your own vehicles. To start one,you would have to do /c yardsale and after that ,you would have to do like /c putitem and then type the name of the product.For example:
/c putitem [item] [amount] [buy price]
And if you accidentally put something you don't want to sell you could use something like /c removeitem and type the name of the item.For example:
/c removeitem [item] [amount]
After you're done ,you'd have to do /c beginyardsale after which a /c ad saying that someone has started a yard sale at their property.Like:
[ADVERTISMENT]PLAYER has started a yard sale at Vice-City-Mainland-Little-Haiti.
After you arrive at the location,you could see a floating icon with a huge "i" (the ones in the business props).
After picking it up,it will show the list of the items for sale.
Thats all.