The most important thing your friend can do is find a reputable brokerage company that has a training program and a mentorship program. The technical skills (such as valuing a business) can be learned fairly easily. Only a good mentor can teach the brokerage aspect (i.e., negotiating an agreement between two opposing parties, anticipating deal challenges, then managing the transaction to a successful closing). There are a million terrible brokers and only a few good ones - your friend needs to find one of the good ones to learn the business.

Strongly agree with Brad and Bryn's comments above, but I would add that engaging with national trade organizations (IBBA and M&A Source in my case, there are others too) will add considerable knowledge and polish to your freind's offering in the marketplace. As a business broker, all you have to sell is your time and expertise. The classes I have taken and the mentors I have identified at IBBA and M&A Source have made a huge difference in my practice.