The most traditional way to find (and list) a house for sale is via the Multiple Listing Service (MLS). MLS is a service that allows sellers to post listings to many different aggregators and websites to find houses all across the internet, enabling buyers to search across thousands of real estate agent listings quickly and efficiently. If a house is being sold, chances are that it’s listed on MLS.
The main downside of finding houses to flip on the MLS is the high level of competition you will face as a buyer. Given the thousands of people using the service, homes priced under market value are snapped up very quickly, so it’s hard to find a property which truly presents a unique opportunity. Also, you have to be a realtor to access the MLS, which means joining your local Realtor Association. These associations will require fees, about $1,000 or so a year.