In a nut-shell - there are 3 types of DD you need to make:
- Business (that you understand the business completely including distribution marketing channels, growth engines, customer service, how much does it cost to acquire a new customer etc.).
- Legal (let your lawyers do that, and DO NOT PROCEED WITHOUT ONE as there are many aspects to think about that you usually don't even imagine like taxes, anti-trust, money laundering and many more that might be relevant).
- Financial (to make sure all numbers are right and together with the legal DD gives you a real picture of the business).