Flipping a house is complicated. Next to the purchase price, estimating the cost of renovation is the most important factor for you to consider. There are actually two issues in play here: 1) what exactly will you change, repair or upgrade, and 2) what will this cost. We'll tackle each of these separately.

What to change?

There will certainly be homes that you could buy that will lend themselves to major renovation. Things like an addition, a second floor, a porch or patio, an additional bathroom, etc. We have seen homes that, with a major addition, could possibly net $100,000 more than they would without it. But when considering major additions, you really need to take several factors into consideration. First...