需要哪些手续和文件？
根据我有限的知识，至少要以下文件：
Assignment of XX% (the percentage you will get) ownership interest from XXX (your friend) to XXX (you) (date of execution)
Bill of Sale of XX% ownership interest from XXX (your friend) to XXX (you) (date of sale)
Buy/Sell Agreement (agreement effective date) - this is to protect you both
Consent to Transfer of Membership Interests to XXX (date)
Amended Company Agreement (approval date) - this is to document the membership change
Employment Agreement with XXX (your friend)
Employment Agreement with XXX (you)
Membership Certificates
我的建议是，朋友归朋友，business is business。还是找个律师来弄好应该有的文件，以避免将来不必要的法律和利益纠纷。Hope this helps and good luck to y'all! :)
