As you may know, you can donate 35 dollars[USD] to get a costume house car of your choose. Saying that, I have made this thread to in-form you on what cars/airplanes/boats/helicopters/motorcycles you are not allowed to get. The general rule for buying a donated car is that the car of your choose cannot have any guns or weapons on it that can harm or kill other players. Also some cars/airplanes/boats/helicopter/motorcycles are restricted to factions only.
Airplanes:
Rustler
This airplane has 2 weapons mounted on the wings of the plane.
Hydra
This airplane has rocket launchers on the wings and shoots flares.
Boats:
Predator
This boat is restricted to LSPD only and has 2 guns mounted on the front of the boat.
Helicopters:
Hunter
This helicopter has 2 wings with rocker launchers on each side and a minigun on the nose.
Sea Sparrow
This helicopter has a minigun mounted on the left side of the ladding base.
Raindance
This helicopter is restricted to LSFMD only and has to weapons on it.
Police Maverick
This helicopter is restricted to LSPD only and has no weapons on it.
Cragobob
This helicopter is restricted to SANG only, and has no weapons on it.
News Copper
This helicopter is restricted to SaNews only and has no weapons on it.
Cars:
Barracks
This car is restricted to SANG only and has no weapons on it.
Enforcer
This car is restricted to LSPD only and has no weapons on it.
FBI Truck
This car is restricted to LSPD only and has no weapons on it.
FBI Rancher
This car is rearrested to FBI only and has no weapon on it.
Police Car
This car is restricted to LSPD only and has no weapons on it.
Police Rancher
This car is restricted to LSPD only and has no weapons on it.
Rhino
This car has a rocket launcher in the middle of it.
S.W.A.T
This car is restricted to LSPD only and has a water canon on the top of it.
Cheetah
This car is restricted to FBI only and has no weapons on it.
Patriot
This car is restricted to SANG only and has no weapons on it.
Newsvan
This car is restricted to SaNews only and has no weapons on it.
Ambulance
This car is restricted to LSFMD only and has no weapons on it.
Firetruck(s)
These cars are restricted to LSFMD only and one of them has a water canon on the top of it.
LVPD Police Car
This car is restricted to LSPD only and has no weapons on it.
Motorcycles
HPV-1000
This motorcycle is restricted to LSPD only and has no weapon on it.
Note: Any RC cars or trailers are also NOT allowed as a vehicle.
Credits for Pictures and names - http://gta.wikia.com/Vehicles_in_GTA_San_Andreas and http://www.google.com