Actually, when I was offered a sale by my landlord, a friend who is an estate agent handled the price negotiation. Came up with a price that seemed reasonable to both (until legal issues popped up and made it impossible).I think you should settle for a reasonable discount against open market value, something like 5%.
You won't have the hassle of marketing, cleaning up for sale, an empty period before new owner, less risk of sale falling through, etc. They may want to take furniture too which a third party almost certainly won't.
Start with a few valuations and take it from there. It might be easiest for both parties to negotiate via solicitor (but this will cost more).
1-1.5% agents fees plus €4-500 advertising costs are the standard rates. Optional after that are clean-up or redecoration costs to have it looking its best.Roughy how much would it cost too put on the open market Iff12 ?