I'd definitely get the
points charts and try to decide how ofter you will visit as well as what size unit you will need. Unless you live within 6 hours or so, I'd recommend buying at least a full weeks points for either a 1 or 2 BR for the time you think you will usually travel. If you have children, I'd buy at least points to match magic season (summer) for the resort you are buying and/or the resort you plan on staying the most. That means most people should buy at least 220 for an OKW 1 BR and 300 for a 2 BR. For the other on property resorts, the numbers are more like 270 & 350. For every other year, I'd buy between 150-500 points depending on specifics. I'd recommend against buying exactly the number of points you need by the chart unless you're buying enough for magic season in a 2 BR every year for at least a full week. Generally a small cushion is a good idea. That way if they readjust the points, you won't be messed up.
If you have 2 children the same gender, the 1 BR should be fine for quite a while. If they are different gender or you have or anticipate more than 2, I'd look at a 2 BR when deciding how many points.
I think few people who buy with the idea of staying in a studio stick to that plan long term. Many who plan on going every 2 or even 3 years, change their mind when they get the DVC bug. Just make sure this is something you can afford. When I hear about people asking about the minimum, I always worry about them.
OTOH, I think a lot of people have bought the minimum (currently 150) to try it out and see how this will work for them. While you may not be able to add on a few points at your home resort, you can always add on at a resort DVC is still selling. The DI project is coming for 2004 and hopefully Eagle Pines at some point though I'm skeptical. Remember you can always go out and buy more points on the resale market. You could always get your home resort or look at other resorts. Many like owning multiple resorts so they get the 11 month home priority at other resorts.
If you're pretty set on one resort, buy there. Otherwise consider a resale at OKW or BW. You could even do a resale then add on at BCV if you so chose. I hope this helps you.