What you're showing there is an RM motocross bike, not an RMX.
The RMX is the offroad version of the RM, and should have a headlight, tail light, smoother motor. Nevertheless,
If you're getting a dirt m/c to follow your son on, I would not recommend buying a two stroke motocross dirt bike. They're very quick revving and hard hitting, but lacking in torque and ease of use. When following your son, a 2 stroke bike will often be riding too slowly, so this may foul out the spark plug, the motor won't get hot enough to vaporize the premix oil suspended in the fuel, so there will not be sufficient lubrication going to the crank bearings when riding that slow.
I would suggest getting a Simple, air cooled, four stroke dirt bike, one w/ electric start. something like a Honda CRF230F or Yamaha TTR230, with a low seat height, and a side kick stand.
Or
buy the next size up dirt bike (KX85/KX100, CRF150R/CRF150F, TTR125/TTR125L, etc...) that you will eventually move your son up to when he outgrows that RM65, and ride that bike to follow him on.
And, you don't really need a truck (unless you want one) to haul motorcycles. Just get a single axle trailer and put a trailer hitch on your car/SUV.
Thank you.
I was thinking that pix is the one.
However, here's the real one:
I 've never owned a dirt bike for myself, so I 'd like to buy one for a trial first, to see how the thing goes. Then I will decide for better fit.
So I don't want to spend much money for the first one.
In Vietnam, dirt bike is quite expensive.
The one I showed above looks like the best to my budget.
About the truck - that's only thing we can do here. It is not allowed to put a trailer after your car/suv.