How to find out what is important to a seller?

[Zac Boelkow]

   I was casually in negotiations on a duplex. The seller is willing to owner finance. He and his agent and me and my agent have never done an owner finance. Which seems fairly simple enough. At the last minute the seller had his realtor tell us he didnt want to sell any longer. I had the feeling like there was more to the sell than money so I called the realtor and asked permission to contact him personally so he and I can discuss what is goals and wants are. So I have a meeting in a few hours to discuss how we can negotiate the terms so they are mutually beneficial for all parties involved, which includes two long term tenants who are paying below market rent values. I can pay him asking price but I would need to raise the rent  38% which will force the current tenants to move out. I feel like they can handle 15% rent increase and would be willing to stay and be able to afford that. Realistically rent should be raised a solid 23% to be current in my specific market/area. 

   Any suggestions, tips, or ideas is greatly appreciated. I know the seller doesnt need the money and is also concerned for his long term tenants well being. As I am interested in keeping long term established good paying tenants even if I leave a little meat on the bone...