I think I've seen thus mentioned briefly in others but I feel this would be good to talk about in a whole.
I think relationships with NPCs is definitely needed. Doing bad actions could generate bad karma with characters. Like for instance, if you make a bad name at a company you might not be able to enter it and building up the relationship to be unbanned could be needed (through side jobs or maybe money).
Cops that don't like you might watch you closely. At a crime scene this could be devastating. Might need to pay him off to look away or increase your reputation with the police.
Anger a household? Might not be able to search a house any longer making you break in, pay more money, ect.
If you help people out more often, maybe you can get info easier and asking to enter the house becomes much easier.