Poisonluck Jevon

I'm fairly proficiant at modding my own avatars but I was looking for advice on providing my modding services to others, mainly textures. Is there a way to edit the textures of your clients objects/avatars or do you have to purchase the item yourself and would you include that cost into your services or is keeping up with popular items just a cost of doing business? I'd appreciate any advice for pricing or other pitfalls as well!