DarkRP Credits/Purchasable Rank

I know this is probably something really simple but I cant seem ti figure out how to do it. I’ve been in a couple DarkRP servers and you could buy “credits” with real money. With these credits you could either purchase ranks (ex: VIP, respected, Supporter, Donor-Mod), you could buy RP cash with these credits and rare guns. I’m wondering how you could do this. If anyone knows, I would greatly appreciate some information or a tutorial on how to so it. Thank you!

DarkRP Help Thread:
http://forum.facepunch.com/showthread.php?t=1249475

You’ll have a lot more luck in that thread; the same question has probably already been asked, and answered, in that thread.