Part of the equation is why do you want to seller finance while anticipating selling the note instead of waiting for a qualified buyer. If the property or market has problems that require seller financing, the investor will require a healthy discounted yield to compensate for the extra risk. If the market will not support the $125,000 sale price or the down payment was made outside of escrow, you will have a much larger discount and lose potential note buyers.
If you can't use the cash right now and prefer earning interest or want to defer capital gains taxes, meaning there are not any real issues with the property or market conditions, you might get an investor to discount the note only to yield 8 - 10%. A 25% down payment is strong, you will want to review the buyer's credit to make certain they have good credit.
You will also need to check to see if you need an RMLO to create a compliant loan. Developers are required regardless of the number of notes they create. The rules regarding flippers and rehabbers have not been interpreted yet to be definitive as far as I know.