It probably depends on the market. Here in Baltimore there are plenty of deals on the MLS that have enough meat on them to make decent flips that Realtors have ready access to (if they have the experience and systems in place to spot the good deals). In other markets the MLS may be more scarce, so you'll need to rely more heavily on wholesalers and your own marketing.
That said, you don't have to lock yourself into one source. Network with Realtors who have experience working with investors. Get on Buyers Lists of established and honest wholesalers. Send out your own marketing pieces to prospective sellers.
It probably depends on the market. Here in Baltimore there are plenty of deals on the MLS that have enough meat on them to make decent flips that Realtors have ready access to (if they have the experience and systems in place to spot the good deals). In other markets the MLS may be more scarce, so you'll need to rely more heavily on wholesalers and your own marketing.
That said, you don't have to lock yourself into one source. Network with Realtors who have experience working with investors. Get on Buyers Lists of established and honest wholesalers. Send out your own marketing pieces to prospective sellers.