I would separate the two income streams and place a value on them.
1. Is the lot rent for the park.
2. Is the notes on the homes.
They don't even need to be sold together, so I'd definitely evaluate separately. I'd look to see what is left on the note, and look for a discount on them. If they are performing, maybe 80-90% of remaining balance. If not performing, it depends on the home itself really. If it has more value than the remaining balance, I'd look for a 50% discount. Because you will either need to get it performing, or evict and resell. Either way, you have more work, more risk therefore the note isn't worth as much. I wouldn't want the note if the UPB, is more than the value of the home. Let him keep that one.