How do I handle private $ going into an LLC?

I’ve found a private lender willing to invest in my LLC. Any suggestions on how to structure the deal? What should the arrangement “look like”? Most likely I will have an attorney draw up paperwork but I just want to get an idea of what’s involved and any potential problems I can head off.

Thanks

  1. capital contribution (if he takes a membership interest in the LLC)
    or
  2. loan