1st time SB - how to know if my SD is serious?

Heya! I hope you are well! 😊

My 1st SD reached out and specifically addressed that he does not want to meet in person, and I am okay with it.

We agreed on a weekly allowance but it looks like he wants to do it only when a full week of our online adventures wraps up, so not paying upfront.

We just started chatting - like, couple hrs ago. I am concerned of putting a lot of energy for this full week only to end up getting ghosted. Is it okay to ask for some sort of a deposit reassurance? If so - what if he refuses? Thanks!

Tldr; I wanna find a way to confirm that my SD will not scam me and is serious, and we just got started.