Golf just happens to be an expensive hobby. You might want to start off with a mid-priced set of clubs ($200 - $300) to make sure that you really like it (you'll also need shoes, a bag, balls, tees, towels, etc). After you get into it, then step up to the better quality clubs ($500+). But, do invest in a good putter & maybe a driver. They really make a huge difference (at least for me).
As far as the driving range once a week & 18 holes once a month, just price your local places out. In my area I can hit a bucket of balls for $5 - $8, fairly inexpensive. 18 holes, $100+ at our better places (I'm by Firestone which throws off the curve). Make sure you don't need a membership to play at the places you're looking at. I can't even imagine what a membership to Firestone would be. But one of our smaller places was $35k!!! Plus you still pay for your games - the memberships have benefits, but this is where things get expensive. So, about $1600 for the year, just to play (again this is NE Ohio rates.... not the rates you'll see). But we have a little Par-3 down the street from work (only need 3 clubs really) that's about $20.00. Shoes - $75.00 ish (online).
When I learned to play, it was in high school & the rules are farily straight forward. But everyone has a rules book so you don't have to remember everything (buy a rules book too). You could even take a few lessons to really get a good grasp of things. The basics of the game you can learn quickly, just a few weeks to a month or two depending on how much you dive into it. The technique - well, Tiger still practices & refines his swing so that's a continous learning thing. I highly recommend lessons for the technique at the very least. People watch tv & it looks easy - it's not. The swing is actually very technical when you're first learning & bad habits are easy to latch onto.
Here's a site for you: http://www.golfsupport.com/tips.htm & http://sports.expertvillage.com/videos/gol...g-technique.htm
Good luck!