the majority is on road racing in generAL,,, all tracks are equiped to accomodate both nitro and electric. from observation, there are more electric racers than nitro.
tracks gere are capitol speedwaym speedzone r/c raceway, rc speeway in pinagbuhatan pasign and, i think that's it....
as for cost.. well.. i suggest you start with second hand stuff to keep costs at a minimum.. but just as lem said, try to figure out the history of the profucts before buying them.. a good 10-15k i guess to start with..