Starting an REI Mastermind - Format/Content Suggestions?

[Owen Dashner]

For any investors who have either started or are part of a really good mastermind group, I'd love some input on how it is structured. What is the format, how many people are part of it, paid/free, venues, is it speaker led or open format, etc. Any input is appreciated. Ideally what I am going for is not only REI tactical/strategy stuff, but mindset/goal setting/accountability/etc. What do you like about yours, what do you not like?

Thanks in advance!