Maintenance i just bill at the first of the month, for that month. Landscape installs i require a deposit for work thats more than $2,000. So far, knock on wood, ive never been stiffed with this method.
We bill after the month's services, take credit cards, and rarely need a pre payment / deposit for anything other than installs. Installs we get 30% down at contract signing,30% the first day our trucks pull into the site, and the remaining 40% net 14-30 days on completion without a pre arranged payment plan.