I have been doing lawn care, part-time for about a year now. A few of my customers pay on the spot, but most want to be invoiced. I started out mailing hard copies, but have since started using Paypal. This has proven very simple for me, convenient for my customers, and offers quick payment. There are fees involved, but by the time I figure postage, hassle, and wait times, the fees seem insignificant. Anyone else doing this?