It could be that he just doesn't want to see his home demolished for some emotional reason and he'd be willing to accept 0 down and 4% interest over a 30 year amortization with a 10 year balloon. 

Don't make an emotional decision and don't be bullied into commitments that you do not want to make.

If you really reallly realllly want it, I guess you could offer to pay half, but it sounds like your starting to get emotional about a deal and that can be bad.

Emotion is dictating things not business decisions.

This is a great, no-emotion letter.

You can't become emotional about real estate.

Crazy as it seems, sellers in emotional distress and denial over whizzing away their parent's legacy would much rather whiz it away to a local agent who is deeply embedded in their community, who works the soft-serve at church festivals and reads off the bingo numbers at the VFW hall and brings some of his homemade kielbasi to the volunteer firemen's BBQ benefit.Do not discount your local agents who have been eating rubber chicken to pass the card at Rotary events for the last twenty years.

It is good that you have emotions but learn how to control them. 

That isn't to say you can't increase the rent because he's been there for 2 years just do not mention the emotional support dog.Tell him you are moving out and want both units under an annual lease. 

Having a house broken into is so emotionally trying.