Bet means okay, and is often used to agree with someone. For example, if someone asked, Can we go to the pool tomorrow afternoon? their friend might reply with Bet!
As ESSENCE previously pointed out, Perry still holds minority stake in BET+, and works with the network to house a large number of his productions. Perry and BET have been in collaboration for quite some time, as the network helped fund his first feature, 2005's Diary of a Mad Black Woman.