Dear …
I just wanted to take a moment to write to you to express our thanks for the extra efforts you gave in advising __(Name)__ and I with our start-up business. It’s people like you who help to make our world a better place, simple by taking the extra time to ensure that we are comfortable with what it takes to start a business and understand it well. I think we can safely say you are one of a kind, __(Name)__!
You stand head and shoulders above others in the business industry, __(Name)__, and we greatly appreciate the time you took to care. Again, thanks for everything.
Sincerely,