a sugar baby if she's older than you are?

But, in any case, I have heard the term sugar-mama used to refer to this situation, which would make you a sugar-boy, I suppose.

Unless you are under 30 years old.  

But sugar mama would mean that she's got the money and I'm the recipient, which wouldn't be the case

Back home we have a saying "you have to learn to ride on an old bicycle"......even at 39 I suppose I'm still learning things

Everyone knows that a sugar-babe is a young gal who sees wealthy guys for sex on a regular basis.

I assumed a sugar mama was a a lesbian.

No they tend to be rich divorced cougars who keep a stable of boy-toys who they take care of, like us men do with SB's