If it were me, I would rather pay my money to a shop that specializes in repairing BMWs, someone who can distinguish the sound of a failing VANOS from the sound of a loose heat shield, and will run a compression check and look at blowby. The problem is that someone has to take the car to that shop.
I have looked at a few used cars, and I have helped friends and relatives look at a few used cars. I always found that after I had looked at a car and left, I always thought of something else I should have checked. Finally, I generated a checklist so that I would not forget anything. This checklist is only superficial stuff. The owner will be really uncomfortable if a stranger starts pulling off engine covers and removing coils and spark plugs to do a compression test.
What to look for on the Test Drive:
Handling:
[ ] City street handling
[ ] Highway handling
[ ] Two-lane road handling
Suspension:
[ ] Excessive body lean
[ ] Body motion control
[ ] Vehicle directional change with changing throttle
[ ] Noises with changing speed, direction, or bumps
Engine:
[ ] Noise
[ ] Acceleration
[ ] Idle
[ ] Hot restart without stalling
[ ] Visible Sludge under valve cover
[ ] Stored Computer Codes
[ ] Signs of oil leaks
[ ] Modifications and 'performance' parts.
[ ] Belts, hoses, clamps, inc. heater hoses
Steering:
[ ] Ease of operation
[ ] Vibration through steering wheel
[ ] Road feel
[ ] Loosness when moving or stopped.
[ ] clunks or pump whine
Transmission (Manual):
[ ] Clutch feel
[ ] Smooth gear changes
[ ] Noise
[ ] Cruise control
Brakes:
[ ] Parking brake
[ ] Brake pedal pressure
[ ] Brake pedal travel
[ ] Stopping gradually
[ ] Stopping suddenly
[ ] Antilock brakes
What to look for on the Interior:
From the Driver's Seat:
[ ] Do ALL warning lights illuminate?
inc. air bag, check engine, maintenance, ASC,
[ ] Seat controls
[ ] On-Board Computer Display
[ ] Instrument panel clarity/illumination
[ ] Tilt/Telescoping Steering wheel
[ ] All four electric windows (full up and down)
[ ] Sunroof fit and function
[ ] Water stains around glass and sunroof
[ ] Age of map in NAV system
[ ] Other Power accessories (wipers, etc)
[ ] Mirror controls
[ ] Radio, cassette or CD player and speakers
[ ] Heater, air conditioner and ventilation
[ ] Remote trunk and fuel-door releases
[ ] Horn operation
[ ] Interior dome light
[ ] Wiper/washer system
From the Passenger Seats:
[ ] Seat controls
[ ] Strap handles
[ ] Reading lights
[ ] Seatbelt operation
[ ] Folding rear seats
[ ] Rear Seatbelt operation
[ ] Rear defogger
[ ] Visor vanity lights
[ ] Glovebox
[ ] Cupholders
Look for quality of:
[ ] Upholstery
[ ] Headliner
[ ] Fit of interior panels
[ ] Trim and moldings
[ ] Dashboard
[ ] Carpet and mats
[ ] Window Tint
What to look for on the Exterior:
[ ] Paint
[ ] Rust spots
[ ] Tire tread wear
[ ] Bent Wheels
[ ] Damage beneath car (if visible)
[ ] Rusty Exhaust
[ ] Missing plastic shields beneath
[ ] Body-panel dents
[ ] Fit of trunk, hood, and all doors
[ ] Seals around doors and trunk
[ ] Evidence of rust or damage around frame
[ ] Paint overspray around doors, trunk, hood
[ ] Moisture in headlights and tail lights
[ ] Smoke from the tailpipe
[ ] Free flowing exhaust
Check the trunk for:
[ ] Key for Tire Locks
[ ] Spare tire
[ ] Jack
[ ] Lug wrench
[ ] Tool Kit
[ ] Carpeting and trim
[ ] Trunk light
[ ] Secure latching
Try keys on locks and latches:
[ ] Doors
[ ] Glovebox
[ ] Anti-theft system
[ ] Gas cap
[ ] Trunk
Try these:
[ ] Trunk release/catch
[ ] Hood release/catch
[ ] All four door latches/locks
[ ] Headlights
[ ] Parking lights
[ ] Reverse lights
[ ] Brake lights
[ ] Taillights
[ ] Hazard lights
[ ] Turn signal lights
[ ] License plate light