Like Scott said,
I would be sincere, and upfront initially. If you have an address, I would definately go to his house. I would start by saying that I hope I'm not being a bother and apoligize in advance if I am.
I would then say.... I'm sorry about your loss, I'm interested in buying your dad's house. I can make the transaction quick and easy for you.
Then like every sales process, I would immediatley back off for a while and talk about something else for a little while. Try to warm up the prospect a little and find common ground. You might want to test the waters and ask about his Dad. If you were fortunate enough to have met his Dad and you discover that he enjoys talking about him, interject your experiences with him. while he talks... i.e....Everyone in the neighborhood always commented on how nice he was...or how hard he worked...or how fun he was to be around....ect...
Look around his house for pictures, trinkets, anything that you can compliment and get him to talk. Let him talk about the weather, hockey, football, talk about basketball, baseball....whatever you discover that he enjoys talking about. Talk about his job, his Dad's job, military service, community service whatever.
Once you hit conversational pay dirt.....let him talk away. The more he talks and the more you listen...the more he's gonna like you....the better you chances are of putting a deal together. ======Become a POWER LISTENER===
Here's a listening trick that I use sometimes.....lean forward and slightly towards them while they're talking and place your cupped hand behind your ear to increase amplification if a distraction arises while they're talking. Body Language is 77% of communication. He's gonna really enjoy talking to you. (this stuff should be illegal.....lol)
After you find something that he enjoys and have listened to him talk for awhile....slowly bring the conversation back around to the house.
If you can find something that he likes talking about before you even say that you're at his door to buy his Dad's house...all the better....your sales percentage goes up dramatically.
Next step after "Greeting and Warmup"
Have a Great Story prepared to tell......
Everyone loves a good story.
I'm working my way thru school and need to xyz. I'm trying to move close to my Dad. My wife loves the proximatey to xyz and has already started packing. She made me go to 4 different stores last night for boxes to pack. When I got home from work today she had boxes stacked 7' high (make over exaggerated hand motions to show the height of the boxes) I don't know how she done it, she only 5'5" tall.
After a good story go in for a close...
Use the faithful tried and tested....
"If I could, would you".
"If I were to find you a lime green poka dotted hemi head dodge pick-up, would you buy it today?"
Hopefully, in the course of listening to him do all that talking you heard him spill the "IF", part of the equation. If by happen chance you did, then simply plug it in to the above statement followed by: "Would you sell me the house?" or "Could we put a transaction together?"
I remember years ago I bought a house from a guy who's religious belief didn't allow him to make a profit. I had spent a great deal of time listening to this guy. Really nice guy but plum nutzs!!! He told me stories starting from his fighter pilot days all the way up to his current decision which was to sell his house along with all of his worldly possesions and move his family into a commune. I had created a talking monster and coudn't get a word in edgewise. Finally, in a desperate attempt to cut the chase I blurted out........
"I know exactly how you feel but, let me ask you."
"If I could purchase your home in such a manner that you wouldn't make any profit off of me, ...I'm talking about not one red cent....could we finalize this transaction today?"
He replied, "Sure!"
Good luck....I guess I've talked enough....lol