I've started to play GTA V, and I've been looking to unlock the Ponsonbys stores in order to get my characters all into suits. I've managed to locate one of the stores on Portola Drive, but I cannot enter. From what I understand you have to do a mission of some kind, but it's not entirely clear for me when this is.
The last missions I've completed are the ones that introduces Chop and has you repossess a motorbike, and I still have at least one mission available with Simeon (not quite sure how many). What do I still need to do to unlock these stores?
I would like a spoiler free answer, or at least answered in a way that I know it when I see it.