I think that this goes back to a basic financial concept of risk and reward. You accept greater risk in making investments, and in return you expect a greater potential reward. If you want safer investments, you give up a greater potential reward.
Betting on appreciation in the future is a lot riskier than analyzing current cash flow and making an investment based on that, but it could end up with a much greater return as your family friend noticed.
It all comes down to what is your risk tolerance, and what are your goals.
If you own something directly in a major metro, and it is not too much of a financial pinch to prevent you from steadily adding to the portfolio in a less expensive area, keep it. Maybe you won't be able to scale as quickly by keeping it, but its one of those things that you may not ever be able to get again. Hang on if you can, steadily expand elsewhere. When its time for the very big pay day down the road, you'll be glad that you waited to pull the trigger.