Sellers may be willing to finance if they percieve that as the best solution for meeting their needs. For instance, if a vacant home has been sitting on the market for some time the sellers may be in a situation where they are paying two mortgages, taxes and upkeep. This would be draining for them. An offer to buy the home using them as the bank may be favorable. Keep in mind the terms of payment would also have to meet their needs. Down money may have to cover the real estate agents commission and any other costs they have. Be very careful that the terms of the loan also meet your needs. We would advise you to have an attorney look over the contract before any party signs.
As you look around for seller finance opportunities, you will be told no more than yes, but success will come when you can develop the best solution to the sellers problem.