Start by going to:
http://rccombat.com/rcca.asp
Rules for several classes are posted there. There's also a topic forum on that site with everything anyone might need to know about Combat stuff.

For inexpensive and simple designs, go to:
http://www.spadtothebone.com

Take a look at those sites, decide exacly what style of Combat suits your group best and you'll be off and running.

HTH,
D