Hey, so when I go on duty and try to buy something from a convenient store, it says I have insufficient funds. Franklin, the character I'm playing as on duty has more than 1 billion in his account. Is there any way I can buy stuff on duty?

This is the same case for me too. We need to wait for an update, or a plugin/script to enable this. 

For some reason anything money related is bound to the player model, and not which protagonist you start off with before changing the model, meaning that once you switch to a cop model, or even an EUP Online model, it is no longer possible to purchase anything, and I somewhat doubt there's much that can be done about that.

 

I don't see why you'd want to buy stuff as a cop though, the basics are already supplied automatically when going on duty, and if you ever want a different weapon, more ammo or max health you can use a trainer or even the RPH console.

I can see the use of it. For role play purposes  - it can be fun to stop buy and buy a cup of coffee and something to eat. :)