Zack's place is a nice option for staying in a well-connected cheap room. It is more on the side of a professional hostel, and you share the room with one other, and there are (from what I could count) up to 8 other people in the apartment besides that (this was not so clear from the picture when I saw it). Depending on your luck, it may therefore be noisy, common facilities may be busy/not shining clean, but that's true for any hostel.
You are near Colma station, which is well connected, albeit less so than the nearby Daly City station (one step over).
Zack is a great host, though you may not see him, as he responds swiftly and is very helpful. Check-in is a breeze due to the nummeric lock.