I thought I'd saved this one but I cannot find it.
Two teenagers - end of highschoolish - have known each other as friends for a long time as usual.
The female of the duo proposes an experiment to the boy wherein they'd experiment through the various bases.
The story begins with the boy working out on gym equipment in his garage.
They get involved with the owner of a sex shop and BDSM elements enter the story.
They eventually progress to college, IIRC, and go live in someone's outbuilding. Except that someone is a widow who happens to know the sex shop owner, so they all end up involved with each other.
At the end of the story, the girl says to the boy that as a further experiment they should have children.
Can anyone help me find it? I just spent a solid twenty minutes looking through epubs.
Thank you!
Edit: SOLVED, The Benefit of Friends, MemoryHeap