You ask how you can turn $25,000 into $50,000 using fixer-upper real estate as your method. A few years back you'd have only needed to buy a fixer-upper, spend $50 on paint, mow the lawn and relist it. But because that was possible then doesn't mean it still is. Today you will need 25% down to buy an investment home--so if you already have a house, then the next one you buy will be for investment.
You will save yourself and those of us who try to answer these questions alot of time if you ask this question of a reputable mortgage banker. Buying auction properties and trying to lift cash out of properties that may or may not have real market value is not something for the faint of heart or the freshman investor.
My suggestion is you take your $25K and invest it in a $100,000 home in Florida that you can rent out to your snowbird neighbors and use yourself. Today trying to make money in foreclosures and fixer-uppers is risky indeed.