You could try the plumbing dept. at Home Depot. Ask for drip irrigation systems. I've bought several systems there for my clients. Let's see, the timer was $30. Runs on a AA battery, I believe. Put the timer on the spigot. If you have to share the spigot with other gardeners, you can just install a splitter. About $5. (I think one of these systems would be maxed out watering a 20x20 plot) You could buy a brass splitter that would turn one spigot into 4 for about $20. You can put a timer/system on each one as long as none go on at the same time. Where were we? Oh yeah. You've got the timer. Run the hose to the center of your bed. There you will screw on the drip manifold. (Home Depot plumbing) This has 8 or 9 smaller outlets that you attach your drip lines to. Manifold is probably about $15. The line is cheap. Get a lot. Once you see it all it will make sense. Ya know, I just thought of something. You could just use a soaker hose with the timer. I was installing these systems for potted gardens where soaker hoses wouldn't have worked. Or you could go the super cheap route and just dig trenches between the rows and/or plant you plants on mounds. Then just let the trench's fill up. That's a very effective system that has been in use for thousands of years.
Back to your questions- lets see, Can't very well till with drip or soaker systems. Drip lines can freeze, but not the manifold. Both systems are easy to pull up & store anyway. No maintenance worth mentioning. Just adjusting the timer per season. The only problem will be figuring out how much soaker hose or drip line your water pressure can feed. At worst you may need two systems on one faucet running intermittantly. All my customers give the drip high praises. The reduced water consumption is staggering. Hope that helped. Kelly lushlandscaping@yahoo.com ;)