I mentioned in another reply that I use Daz 3D for the renders. I buy the majority of my assets from their store, everything from figure models to environments to props. The adult assets all come from Renderotica.
I buy full models, and then I edit most of them by combining multiple characters and using shape morphs. I want all my skin textures to reach a certain quality level, so often I'll use/edit a base figure asset and then apply the skin from another figure, including sometimes female model textures. I also change the eye textures to be more realistic, and when I give them hair I often retexture it as well with a more natural shader. And then there's adding the dicks—making sure the skin color works, editing the shape so no two dicks are alike, adding pubes...
Some figures take very little time to create, particularly if they're more or less ready to use straight from the box, as it were. But for most figures I spend a lot of time reiterating before I'm happy. The early models like Connor, Marco, Matt, Riley, and Leo went through a lot of versions before they were done. But even new characters, like the 14 new side characters who'll pop up during the frat party, still take quite a bit of time to make. That's just me being nitpicky however ;)
Now, you definitely do not need to do all this. I'm just going for a specific visual style. You could 100% buy a figure model (only on sale, never buy full price!), add a hair asset, and add clothes, and then you'll be set. But the above it is the basics of what I personally do :)
