I would try and keep it informal - just establish a relationship and call to ask advice from time to time. Setting up the paperwork for something formal with s

I would try and keep it informal - just establish a relationship and call to ask advice from time to time. Setting up the paperwork for something formal with shares changing hands is just another hassle you'd be better off not dealing with. If they do want equity as compensation, then tell them they're welcome to invest in your company, take their money, and treat it like any other angel investment. Angels are expected to automatically provide advice and introductions - that's part of the package.