This article explains how to give players the credit card swep by default.
First of all you will need darkrpmodification if you don't already have it: https://github.com/FPtje/darkrpmodification
Go to addons/darkrpmodification/lua/darkrp_config/settings.lua and scroll to line 339
Add weapon_ch_atm_card to the table GM.Config.DefaultWeapons
Restart your server and you're done!