I can't say about CAD's ,never used them. Sketchup looks fun thou.

For all the regular 3D app's if you just make ya final meshes with out any nGons your never half to worry about it .caved or vexed.

Renderosity is a lot cheaper then turosquid .So just cause you made it for Poser doesn't mean they bought it for Poser. Any of the main app's won't care if it's caved or vexed. they will consider nGons a bad thing and return your mesh n won't buy from you again. If they want a sub dividable mesh then they expect it to be 100% Quads. If it's for games Decimate makes 100% Tri's.

So all meshes should be 100% quads "sub dividable" or 100% Tri's. Not my rules these are the main app's rules.

============================================================ 

The Artist that will fight for decades to conquer their media.
Even if you never know their name ,your know their Art.
Dark Sphere Mage Vengeance