The premise kinda reminds me of
Oujougiwa no Imi o Shire! except here the female lead isn't connected to him from the past.
"It's fine if you want to embrace me just for sexual relief."
So basically sex friends with her additional objective of getting pregnant. It's not even a breeding "kink" for her, it's very possibly a one and done thing just to get that child she wants, who she intends to raise alone with the savings that's burning a hole in her pocket. With that kind of thinking I'm surprised she didn't just ask for his semen in a vial for artificial insemination.
The thing is that because they are not in a romantic relationship, before he commits to what she wants he also has to realize the possibility that they're also not going to be "exclusive", which is a given in normal romantic relationships but not in a potential FWB arrangement like this. Is he fine with that? If he is, then go ahead and say yes. There's nothing he can do if she one day says she wants a second child with another man, since they're not even dating and they don't belong to each other. Or if he fails to get her pregnant, she can also look for someone else for that first child she desires. He can't even call that "cheating" because it isn't so falling in love with her now is a mistake; better if she falls for him first.
Anyway, I feel like she's carrying some serious past relationship trauma that caused her to strongly push the idea of romantic relationships away. If this goes down the expected route of sex friends become lovers, it'll surely be something he'll help her with which is when we enter the "I can fix her" phase.