I second the late 80s early 90's Corolla. They will run forever on just an oil change. Dirt cheap, easy insurance, and get great mileage. That little 4banger is pretty solid. My grampas got one with 250k miles, gets as good of mileage as the day he got it, and runs every bit as well. I totally expect another 150k or more out of it.
I haven't looked into Buicks...but if you can find a newer one for that price ... look into it. The engine is time proven and strong. And if you can find a supercharged one, thats even better

.