It bugs me to buy these because by the time you are able to afford them there's no point in grinding for the money it takes to recoup costs. I imagine (but do not know) that income generation from these is just a stat buried in some RPF, but I can't find it.
Is there any way to enable purchasing properties (income and vehicle storage) before the Nervous Ron mission? I know I can set the owned variable with an internal variable editor or external save editor, but not the same as playing the game.