Tenderloin, I mainly looked in the Russian Hill / Marina / Lower Pac heights areas for private 1 bedroom situations in 2/3 additional roomates. I ended up going for a place in the Presidio. For the most part the opportunities I was seeing were for subleases where a tenant moved out hurriedly, which seems to be VERY common right now.
FWIW all private room + 2/3 roomate situations were in the range of $1200 - $1500 vs. my current 1 bed room apartment (no roomates) @ ~$2800 previously.
I worked in the TL for three years and went on a few dates with a girl who lived there. The people in actual apartments are fine. People in SROs not so much, people on the street can be a problem. The needles, urine, feces are real. The attendant at the lot I parked at said he thought he'd be dead within six weeks of taking the job, but in my time there, I think he was only assaulted once (it was more jarring than injuring). One coworker got slapped by one of the crazies, another assaulted. Oddly enough, my car did fine. I've street-parked it around Turk and Jones and picked it up at ~midnight with all my windows intact. As bad as the TL is, it isn't Bayview. I'm always amazed at walk from with Powell to Civic Center, Geary to Market, or west from Union Square; how quickly it changes is incredible. You also see scared, lost tourists a lot because of that.
There are some interesting restaurants there, and you're actually close to a lot of things. If you're living there in a secure building with a secure garage and can mostly avoid the street, it's tolerable. I wouldn't make a habit of casually walking around the block or stumbling home drunk. If you're paying attention and walking with intent, you're generally fine.
Not weird - though its really just the same as downtown SF: 2-5 days a week you will have some combination of a screaming and manic individual immediately in your walking path, see someone injecting themselves immediately in your vicinity, and nearly (or actually) step in dog/human poop. It by no means is the end of the world but over time it wears you down and desensitizes you to the point of completely ignoring all homeless activity always.
After being here for ~2 years I would not recommend the TL because the cost savings and walking commute to downtown are not enough given alternative choices.
If you need to save money you need to move further away to realize real savings, there are too many hidden fees living in the city.
If you have money you'll want to either live in 0-commute distance i.e. near the embarcadero or in literal downtown, or live in the Marina / Presidio / Anywhere else and have a 15 minute drive in.
FWIW all private room + 2/3 roomate situations were in the range of $1200 - $1500 vs. my current 1 bed room apartment (no roomates) @ ~$2800 previously.