Valentine’s Day is creeping up … and while couples are busy emptying their wallets, Lou Young is waving a financial red flag.

We caught up with Lou at Druski’s “Coulda Been Love” Season 2 event Wednesday, and he told TMZ straight up — fellas need to chill before they blow the rent money trying to impress. Why? Because March 1 is looming … and rent waits for no one.

Catch the full clip … ’cause Lou elaborates on his message — spend what you can afford.

We also hit him with the ultimate IG question — is it a red flag if a guy won’t post his girl? His answer might raise some eyebrows!