>>3733451Boudoir is mostly about the model, the lighting and the environment. Don't stress out about the gear. If your concerned about squeezing every bit of sharpness, you'll get every imperfections and hair on the skin. Just go with a 35mm or equivalent, maybe a 85mm on top of that. You mostly need to be prepared (read posing guides) and make your model comfortable.
One good tip is to go from naked towards lingerie. The opposite leaves marks on the skin.
>>3733426M42 sure are cheap, but zoom lenses are mostly pure shite. Go for primes with a brand, like Zeiss, Takumar, Yashinon...
Try to find a Jupiter-11, good portrait lens.
The Sigma mini zoom f3.5 39-80mm might be good enough.