Side Business
Side Job, Side Gig
noun
A side business is a side business.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
副業で、中古のカメラを売り買いしています。
I buy and sell second-hand cameras on the side.
私のカレは副業でネットワークビジネスをしている。
As a side gig, my boyfriend works for a company using multi-level marketing techniques.
社員の副業をオッケーにするべきだという彼の提案は、一考に値する。
His suggestion that employees should be allowed to have a side job is worth considering.