I cheat the game and buy cars with a lot of miles already on them ;)
Dodge RAM van, 315K miles
Saab 900, 320k miles
Saab 900, 250k miles
Nissan Sentra, 280k miles
Jeep XJ, 200?K miles. Don't recall what I sold that one at...
Toyota Sequoia, 190K miles
Toyota Pickup, 240K miles
Current: Pontiac Vibe, 135K miles, adding maybe 3K miles a year... so that one is going to take awhile.
All of them except the first Saab 900 and Ram van were sold in running condition