Get some experience first by Fixing roofs and exteriors so you don't have leaks, have an electrical contractor inspect electric panel and work, as many foreclosures have electrical issues, same with hvac. Gut Carpets, fix rotting wood, bleach can help with odors, fix and paint walls, do hardwood and tilework, then get new carpets. and List with me when your ready to sell. If you have mold anywhere, beware of the dangers of mold remediation such as mycotoxins released by killing the mold and not removing properly. A remediation company is always suggested as mold is nasty stuff. Can cause all sorts of ailments when removing and killing. I used to work as an environmental technician, so I know the dangers. Be carefull around ductwork as well, especially in older homes, where asbestus was used back in the days. If you see it, get it removed by a professional.
But back to the question, Starting a business doing this will require licensure, contractors insurance, and many bank REO management contacts, as most homes aren't listed until cleaned out. Good luck with finding those contacts. Lets say there are 100 foreclosure on the market, fannie mae owns 20 of them, and the other 80 are different banks. While it may be a great business to get into, the obstacles of starting this business can be high. But keep in there, 80% of businesses started just after a recession succeed. Good luck to you and happy bank hunting.