I've had this twice so far, once from Nancy Landgraab (very in character, if I may say so) and once from one of my own played sims, who apparently had crossed a threshold to get recognized as "rich" by the game (he isn't rich, he just currently lives in a spa hotel). In both cases I couldn't see my sim agreeing, so I turned the caller down. I have other sims, who'd possibly found the offer worth considering, but they didn't get that call.
From the way the possible answers were formulated, it was very clear that turning this offer down was the correct choice and accepting might lead to at the very least awkwardness. That's why I don't have a problem with it.