For a sedan, and a need for space, 2002-2005 Cadillac Deville ($3000-$9000 depending on miles). After all, they have Stabilitrak, front and side airbags, more responsive steering than older Cadillacs, ABS, heated/cooled leather seats, huge trunk, and gets 25mpg hwy with the reliable Northstar V8. Pre-2000 Cadillac (Sedan) Devilles required high-octane gasoline, but the 2000 and afterwards Northstars *prefer* high but will run on regular. They have OnStar, but since it can't be upgraded (aka dead), you can buy a device called BlueStar, which upgrades it to a Bluetooth device only.
A great small SUV, slightly more expensive, is the first generation Cadillac SRX (2004-2006). Plenty of space, plenty of state-of-the-art safety features, Rear-Wheel Drive (it's "sister" - the Chevrolet Equinox - has Front-Wheel Drive), and if selected, two-row sunroof. I've seen them around $15k-$20k, with high-mileage (over 15000mi/yr average) as low as $9k. AWD is an option.
I do not suggest the Escalade line, as you can save thousands by buying a GMC Yukon Denali (practically identical options). Of course, with the huge trucks, you get diminished MPGs and low resale value (aka waste of $$$).
If you haven't figured it out, I am biased towards Cadillacs.
TS