head on straight

[Jimbo]

Помогите, пожалуйста, перевести.
I'm in a relationship where he has his financial head on straight.

[Asseveratio]

up.. ну помогите же

[foxtrot]

м.б. это имеется в виду: [have your] head screwed on straight
have your head screwed on (straight/right) informal to be sensible and able to deal with difficult situations:

[mahavishnu]

Он ясно дал понять о своём отношении к финансам, но можно и получше.

I don't want to be the one who hurts you
I don't want to be the one who fails
I'm keeping my head on straight
So you can trust me again

[mahavishnu]

А вот ещё варианты:
I'm in a relationship with a financially responsible man./I'm in a relationship with a fiscally responsible man./My [boyfriend/fiance/etc.] is [financially/fiscally] responsible.

The person I am [dating/seeing] is (very) frugal./My [boyfriend/fiance/etc.] is (very) frugal.

Slang: The person I am [dating/seeing] is money-smart./My [boyfriend/fiance/etc.] is money-smart.