I'm always confused about "overly promotional" here. I think many people are so we tend to be "under promotional," not even clicking on an ad that might be pertinent to our own lives! That being said, I never link to a business more than once in a hub. If you were talking about this person's experience developing his company, i.e. chossing the name, getting inventory, deciding on suppliers, etc. and then had one link there, I would think that's ok. However, I found that writing to one of the staff involved in hubpages always results in a clarifying response. It takes awhile to find out one of their email addresses, but if you go to the help pages, etc. you will be able to.
It seems to me that it might be safer and more flexible for you to start a blog at blogspot.com (blogger.com) with google. The templates are easy and it seems as if promotion is not an issue. My friend, a psychologist who just released a book used Wordpress. Even if you have only one article, it might be helpful for your friend. Google will pick up the keywords. THEN if you write a GENERAL article about business or shoes, etc. you can always link to that article on blogger AND always link blogger to hubpages.
How nice that you should do this. I wish I had friends and family who would be willing. Somehow people seems reticent to do that. That best things you can do for your friend are to mention his business in tweets on facebook and often. Also, buy one of his handbags and wear them, that's the BEST advertising. Be sure you have his card with you so you can tell your friend. If every friend I have would buy just ONE product from me I could get a little bit of money which would help me make more.
Let me tell you the story of a friend of mine who is a watercolor artist. I could never afford her paintings, but always wanted one. I was just starting my company creating a children's card game based on a game I had played when little. The decks were something like $5.95. One day, I was admiring her lilac water color and knew I couldn't afford it. She said, "Billie, I'll give it to you." I told her I couldn't do that, so she said, "Ok, I'll buy 40 decks of cards." "Marija, what in the world will you do with 40 decks of children's playing cards?" "I have friends, I have family, there are Christmases and birthdays," she replied. That was 25 years ago. Will I ever forget her kindness and support? Never!