I usually give anyone moving out of main played family half to all of the cash money depending on money situation at the moment so they can get comfortable home set up
(well unless family hates them then they get none and get to eat dirt in tent)
(or if their spouse they move out with happens to also be extremely rich they probably do not need as much)
but that is because main heir usually gets the house and all objects in it and they usually have way or another to gain quick money from it
+ since we got vault with get famous i usually keep separate fund in one for any sim that I might want to move out later