On the face of it, based on the numbers you provided, this looks like a solid deal to me. You're projecting $30k/yr income on a $255k purchase price, which is about 12% cap rate. Pretty good, especially with financing, and double especially if the seller will also finance the down payment.
The only red flag that I see is that he seems worried about you defaulting on his money, and the property not being worth enough for him to get paid back. That's a valid concern with the 3yr amortization (he implied) on the second which kills your cash flow. As Thomas Quinn noted, just the payment on that note is $1272/mo, and the first is likely to be around the same (and you need to know). That's break-even cash flow. How would you make payments in bad months? Do you have any reserves? Can you get him to give you a 7 or 10 year amortization with a balloon in 3 years?
How about taking on an equity partner that's got $40k? How about wholesaling the deal?
Bottom line, you've got a good deal (on the surface), but need money to execute.