One of the biggest things is how motivated he is to sell that thing. The more motivated he is the better you can get your terms and make it make sense to you and what your looking for as well. He is old and doesn't want to wait long for his money so keep that in mind for what your purchase price will be, the terms you use and then how long until your note is due. You don't want to get stuck in a situation where you can pay off the note. I put together 4 year notes to older sellers and give them a higher purchase price than I would on my all cash offer. Keep in mind that Im a SFR guy so your situation/property is a little different. I will usually make purchase price 20% off the ARV, set the principal amount to never change each month for the 4 years and then have 1-2% interest on the remaining balance due. I purchase the property as is but my purchase price could change due to property condition. I make my play in the cash out refinance option so I put as much principal into the monthly as possible and have tenant monthly payment cover principal, interest, taxes and insurance. The rest is on me, but in 4 years with basic market growth, keep in mind im in California, I will do a cash out refinance and get apx 70K tax free money out of it and still hold on to the property. If the market turns I still can do a cash out refinance and then do it again when market recovers. Pretty safe deal for me. Remember, this is a SFR in Southern California, but maybe this idea will keep your mind working to put something together that makes sense to you and your seller. Gather as much info from your seller about the property and use it to your advantage to present your seller finance offer to him. Anything that can help him make that decision with you. Spreading out taxes, collecting the same income as he is now from it from your monthly payments if he does the deal with you, etc etc. I LOVE SELLER FINANCE DEALS!!!!! Let your mind work and get creative and talk to the seller about it all till you make it work. If not then move on