I had a terrible experience "onboarding" with Brex last year. They actually "approved" my bootstrapped startup and sent me a physical card only to rescind it a shortly thereafter, because--even though we met the funding minimum--it wasn't "professionally invested" on further review. Bootstrapping apparently required a $1MM minimum.
Here's what they told me:
"While being professionally invested is not a requirement for the Brex card with monthly payments, without professional investment, the minimum cash balance requirement shown in connected accounts is $1mm. If you're able to provide proof of XXXXX's professional investment, the minimum cash balance requirement shown in connected accounts is $50k."
Left a really bitter taste in my mouth. Won't ever use them.
Currently banking with Mercury and love it BTW.