Here is a link that you can go to and download many of the Daz base figures for FREE. It doesn't included V4 though, but many others.

http://www.download.com/3000-20-10579249.html?part=undefined&subj=dl&tag=button

You will need to buy the head and body morph packages for each figure if you want the ability to use character addon packages.  Those morph packages are available at Daz.

Here is a link to  a FAQ for V4:

http://forum.daz3d.com/viewtopic.php?t=57553&sid=744c4589785daf79f55374fdb46b78f9&flatnum=1

Here is an exerp from the FAQ regarding using character addons for V4 and V4.1:

Quote - Will new morph packs require V4.1 or will they work with V4?
It depends on the morph pack. If the morph pack uses the ExP techonology, then V4.1 is required. If it uses the older injection channel technology (loading into PBMCC or PBMDC channels), then it will work with V4 as well as V4.1.

The V4.1 has some extra morphs, but they are largely the same.  So many will work, but some won't. It all depends on how the vendor created the morphs.

Some of the Millennium figures can share clothing and textures with each other. Here is a thread that shows which ones:

http://market.renderosity.com/mod/forumpro/showthread.php?message_id=2682279&ebot_calc_page#message_2682279

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi