@Will Jimenez I think you need to factor in the costs the minimum amount you would pay to close. Title Insurance, Deed Recording, etc... Probably around $2500? That is just a rough guess. There are lots of advantages to the buyer in a seller finance transaction if structured right. You could close this thing fast and easy in theory. A few considerations which I am sure others would advise you:
1. I wouldn't do it without a good RE attorney to, at minimum, look over the contract for any glaring potential conflicts or issues.
2. I would want to determine if the current lienholder has a due on sale clause. People says its a rare occurrence for lienholders to call the note as long as they are getting paid, but they have a right to call the note due in full if they found out the owner sold it to you in a second lien position.
3. One big advantage of a seller financed note is that, in the future, you can try and negotiate a lower payoff amount If they owe what its worth, you don't get that extra bonus in the future.
I hope this helps you in some way.
Best of luck and keep us posted if it comes together!