Money, transportation, housing, referrals/interviews/jobs, a good time with safe people away from an unsafe but currently inescapable situation. Sometimes verbal or written, but that can be just what someone needs. I've personally received a few lifelines.
While those things are great, they're also one-and-done transactions. All the other person needs to do is say thanks and be appreciative.
Building friendships is actually harder. It takes more time and more effort, on many separate occasions. And there's no guarantee it'll be worth it, either.