Buy, renovate, rent, refinance - Lower income areas

[Adam C.]

What are your thoughts on investing in lower income areas? Not horrible, just lower income, downtown. Pros? Cons? Problems? Good idea, Bad idea? A good friend of mine just started buying properties in lower income areas to buy, renovate, rent, refinance, pull his money out, and hold. Then do it again. He hasn't done it long enough for me to see results. Any thoughts?

We're looking in St. Louis primarily