Ok, thanks for that, gotta get more bucks to get some slaves
I am still writing the general guide, as the wiki is spreading those infos all over the place currently, but as a rule of thumb: with very few exceptions only female fighters, that have an actual name before you start a fight, are worth keeping and might be a slave with a quest. Anyone else is just a 'generic' one that might fill some household position, but doesnt come with extra quests.
As things are currently, not keeping any 'generic' ones, is kind of the best approach, as every single person in your household adds to food consumption, without helping you quest and location wise.
As for being able to acquire those with quests: Income from businesses and household requires huge investments first, before they make any notable dent in your daily income. Thus selling those 'generics' is your main income in the early stages. Either add them to your household first and try to sell them to one of the slave markets. This is usually the best approach, if you dont want to cheat, as most of the time the market prices are going to be better than what the quick sell price is (there is some method to which one of the markets you offer them to. Experiment and you will find out yourself which is best for which slave type). Or use the cheesy F5-method while in the slave process window, until the sell price is somewhere upwards of 5k.