GO OUT (1), LET IN FOR

go out (together), (with somebody) = go on a date with somebody, have a romantic relationship with somebody
examples:

• They had been going out together for three years before they got married.
• How long have you and John been going out together?
• She used to go out with Susan 's brother but they broke up.
• My brother has been going out with a girl he met at the train station.

let (myself) in for = put yourself in an unpleasant situation
examples:

• When I gave him my phone number, I didn 't know what I was letting myself in for. He kept calling me and asking me out.
• When I lent her money, I didn 't know what I was letting myself in for. She pretended she didn 't owe me anything!
• She didn 't know what she was letting herself in for when she invited Tony and Jake to her party. They drank too much and caused many problems.
• When they took that loan they certainly didn 't know what they were letting themselves in for.
• So he has decided to go to law school? He is letting himself in for a lot of work.
• I hear you are going to build your house yourselves. You are letting yourselves in for a lot of work.
• You trust him? I hope you know what you 're letting yourself in for! He is not to be trusted.
• If you lend him your father's car, you 're letting yourself in for a lot of trouble. He is a careless driver.
• If I had known what I was letting myself in for, I 'd never have signed the contract.