to be down

an expression of interest and approval of an idea that one hasn't considered before, or as to hint that you want to do something that hasn't been suggested yet.

A: I never been with a dude before, i am a little nervous.

B: You want a hummer?
A: Yeah, I'd be down with that.

or

A: I just can't think of what to do for your birthday.
B: I'd be down with a pair of diamond earrings.
A: ok!

Verb to be down

i'd be down
you'd be down
it'll be down
we be down
they down