[jerry56]

I haven't been doing it very long myself. You kind of have to decide
A. What you want ie dump truck, loader, excavator ...Tractor and trailer...
B. How much time do you want to put into building something.
C. how much you want to spend.
A fully hydraulic excavator or loader will set you back about $2-3K at least, a Tamiya grand hauler and trailer close to 3K...

I can't afford that right now so I convert Tonka trucks and Bruder toys to RC, it has it's draw backs though the Tonkas are fun but lack detail, the Bruders are a very tough plastic but you can't dig in hard ground with them. But if the soil is loose or sandy they are fine. The Tonkas and Bruders require some time to convert but it keeps the cost down and it's kind of satisfying when you finish one. There is also a line of Chinese toys called Huina or TopRace that run from $50 to 500 ot 600 depending. And they all have their pluses and minuses.

SO bottom line decide what it is you want and the folks on this board will help you sort it out.
There are folks that do a great job of building some of the Bruders for other people, just google Bruder conversions and look for SmallHaul