You can set it up how ever you like i know with WERA you have three guys and one alternate but you can only change the alternate 1 time. Motoseries is event to event with up to five riders. I can tell you we split all costs three ways.... entryfees, tires, gas, parts(ie pads oil filters). You crash you fix. Or you can say the first 500 is rider resp. and anything over that is 3 ways or vice versa. I know the initial expenses can be great if you are buying spares. Which you should since you need to get back on track after a crash. I have 2 sets wheels, clip ons, sub frame, levers ect.. I have been racing 13 years and have seen it all. But its always best to get it in writing. I have been stiffed with upwards of $3000 in repairs.