ahh i've always wanted to make one but the parts are so expensive. $80 for an esc, $200 for 2 motors, $100 for a battery...
wow.
i don't even have that much grass to mow!! 
Just be happy your not into racing rc's in spec classes.
esc $200
motor $80
batteries $80
tires $50 every 2-3 race weekends inless you tear one
chassies $200-500
servos $60-80
Race fee's
1st class $15
2nd class $10
3rd class $5
+ travel and roar fee's if you race roar. if more ppl just got interested it wouldn't have to be such a overpriced money grab. but since rc is not nearly as popular as it was companies need to spike prices to make a profit..