I haven't used a footprint in many, many years. Even with really light silnylon floors (SMD Lunar Solo with lighter floor option, no longer available), and with a dog inside, I've never had any problems. Usually some other part of the tent goes long before the floor (the zipper is usually first, but it can be replaced). Just be careful with site selection and preparation.

If you really can't live without a footprint, then use either a piece of plastic painter's drop cloth (will last a trip or two) or get the polycro plastic used for temporary storm windows/doors (will last a season), cut to fit your tent. Just be sure to cut if a couple inches smaller than your tent floor on each side so it won't catch dripping rain and funnel it under the tent. IMHO, there's no reason to spend big bucks on the manufacturers' footprints; they're just trying to take your money.

There's a recent thread on air pads; I think it's in the Lightweight Gear section.

The articles on the home page of this site, left hand column will be very helpful to you when selecting gear.