American English has many everyday phrases for giving, owing and returning favors.
I owe you one. I will repay this favor.
I’ll return the favor. I will do something of equal value for you later.
You scratch my back, I’ll scratch yours. If you help me, I will help you.
Call in a favor. Ask someone to repay a favor they owe you.
Can I pick your brain? Can I ask you for advice or information?
Happy to make an intro. I will introduce you to someone I know.
Much obliged. Thank you. Literally, I am in your debt.
No strings attached. Nothing is expected in return.