[glatt]

A good design of a tent will have a rainfly that covers the entire tent, but is some distance away from the tent, so when the water soaks into the rainfly and beads up on the underside, it doesn't touch the inner tent to get it wet.

Condensation is usually a bigger problem. It's almost always warmer and more humid inside a tent than outside the tent. It's most pronounced in cooler weather, but can happen on a hot summer night too. Moisture from your breath collects on the inside of the tent and condenses there where it meets the slightly cooler temperature from the outside.

The ideal way to avoid condensation is to have lots of ventilation. Again, the best tents for fighting moisture have a nice big rainfly that stands off the tent by several inches. The fly will get wet from rain or condensation, but the inner tent stays dry. Helps if the inner tent has a lot of screening for ventilation.

I have a Slumberjack Trail 3 that is really good at keeping me dry in rain and condensation situations. But it's a heavy 8 pounds. Not too expensive at around $110.

REI probably doesn't sell it. Not expensive enough for them.