It is important when purchasing a vehicle that the vehicle is capable of towing what you require legally. The owner’s manual and manufacturers website will give an approximate towing limit but the actual limits that the authorities will be interested in, is what is on the VIN Plate for the vehicle.
The example below is a VIN plate from a Mercedes E200.
The Top weight 2105kg is the GVW. (Gross Vehicle Weight).
The next weight 4005kg is the GTW. (Gross Train Weight).
The legal Towing Limit then on this vehicle is 4005kg-2105kg = 1900Kg.