IMO if it's just for reference then extra content is irrelevant. You just need a simple nude figure that can be posed and if you can't find a good deal on ebay for Poser Debut then I would really suggest just going for DAZ Studio. It's free and you get the G8 starter essentials for free as well. There's also the weekly freebies and you can slooooooooooooowly build up a library of clothing/hair/characters that way, but if it's just for reference than that shouldn't be a big deal.

Even though you're talking about software for model references may I also suggest a physical figure prop. Maybe one of those wooden basic shape figures or something more detailed like the Phicen/TB League figures. Someone bought me one of those Phicen figures for this exact same purpose and it's actually been super useful in my sketches.