Tony's advice is absolutely spot on.
I would add that FS start ups (I assume this is a fintech?) are proliferating - and can present a great opportunity. But if they arent selling then that equity amounts to nothing anyway. There are a lot of FS startups founded by former bankers of all stripes and hues who do it because they can see a product opportunity, but often hugely underestimate how long it takes to get their products into banks...
As with any start up, dont get blinded by the glamour of equity and the fast culture, look more closely - have they sold yet and to whom? do they have investor backing and are the founders putting their own cash in? What's the burn rate? If it's a product business and most are, can you explain the product simply and without jargon?
Start ups can be hugely rewarding, but go in with your eyes open.