Telling your customer about your payments dilemma to avoid negative feedback is utterly irrelevant since you have now incurred defects anyway for not sending within your handling time. 

Seriously, if you cannot afford the $10 bucks in postage, you should not be selling here. Incur a couple more defects and you'll soon find yourself unable to sell here anyway.

I agree you don't need a printer - I hand write all my addresses, so that's no biggie. It does help to have a printer to print the packing slip for the customer and to make sure everything is ticked off, though.