Friend Claims He Has No Legal Responsibility To Pay Me Back For His Half Of A Trip

To not make this too long, I took my friend to Hawaii in April. The agreement had always been I'll lay it out and he will pay me back. The total was 2600 for his half. Originally I was fine with payments. He did give me $600 a few days after the trip which I acknowledge. But he then moved to Hawaii 6 weeks later just because, telling me he wasn't able to pay me back until he started his jobs in Hawaii and told me he could pay me the 15th of June. That day comes and he still doesn't pay. I ask when he expects a paycheck so I know when he can pay me. No response. So yesterday, June 27, I send a text saying that because it's been over two months since this trip and he has made no effort to pay, I want the full 2,000 remaining balance paid by the end of the day June 30th. He responds once again acknowledging his debt but instead of either saying yes or offering payments, he attacks my character. Claims I was "rude and passive aggressive" during the trip and I was "jealous" after because he was moving to Hawaii and I wasn't (even though I already lived there and didn't have to take other people's money to do so). He said he doesn't have any legal obligation to pay me the full 2k and he will make payments when he feels like it. That if I message him again I won't get anything.

According to my mom who used to practice law, he shot himself in the foot by acknowledging the debt, and that he actually does have a legal obligation to pay me back the $2,000. I am sticking to my word and waiting till June 30th and my plan was to go to small claims court after that. Any advice on how I should proceed would be appreciated

Location: Long Island, New York