Characters begin the game with 0 Assets. For the first five levels of play, characters should typically gain 1 Asset per level. For the final five levels of play, characters should gain 2 Assets per level.
Property is bought and sold at the standard Asset value. So, a character can spend Assets on Property, decide later they don't want it, and sell it for the same amount they bought it for.
For more information, see Player's Guide Chapter 8: Assets and Property.