Made the drive to Car Source Detroit in Detroit — posting notes since this board runs on receipts. They keep around 110 vehicles, mostly budget commuter cars. They were totally fine with my mechanic doing a once-over, which honestly settles half the trust question.
Lot address: 19100 John R St, Detroit, MI 48203. Visitor parking: Lot on John R St. Website: http://carsourcedetroit.com.
Paper side: licensed with the state (looked it up), about 96% of stock has title in hand per the office, and they offer a 30-day/1,000-mile powertrain warranty.
Overall: mixed feelings. Cars looked right but I got two different answers on a title question, and that's my personal tripwire. If you go, get the title status in writing before any deposit.