Your fuck buddies are the intermediary stage between the girls in your iSnatch list and actresses/hookers. You 'train' them in the field they wish to be and when the dial is high enough the next time you 'do them' (if they are going to be a hooker) pick the 3rd option in the list which says, in effect, 'come work for me'. They will then be taken on as a hooker. You will, of ocurse, need a spare slot, else you'll either have to pick a hooker to drop or opt not to take this new girl on.