Immerse yourself in some focused internet searches and read up on the basic foundations of Bitcoin, proof-of-work, blockchain fundamentals, etc... And then after that makes sense read up on derivative works such as Ethereum, et.al. And then go buy a small amount of Bitcoin or Ethereum to try it out and learn how digital wallets work.
If you can follow the high-level math and basic principals of what's explained online - and feel like you would enjoy working this space, then continue on in the interview process. That sort of interview prep will open you up to the most basic and expected questions you can ask back to them, including:
"Can you explain your business model to me?"
Asking that assumes that it's not well defined on their website or has already been stated. If it has, you can ask more specified questions about products, code, customers, reach, etc... Ask how they are going to grow their business from startup to an established firm.
If you like their answers, then it might be worth a shot.
Update - I had a comment under the original question above about avoiding any discussion with this potential employer regarding your financial status. It appears to have been removed. Not sure why, so I'll restate it here: Avoid telling any company involved in finance about your own financial situation ("broke" - your own words). This is probably good advice for any interview, but I had one friend lose his job at a bank for having bad credit. I wouldn't want you to walk into an interview and start off on the wrong foot.