We've had a load of really interesting PMs on this so I thought I'd put some more detail down based on what we've found.
Firstly the domain: we would need a really excellent domain that we couldn't afford to buy... because if we could afford to buy it why wouldn't we...
The owner needs to commit it to this project for a year or include a worthwhile severance package in the event of a sale.
The domain needs to be product rich and be very strong in at least 2 out of: high search volume, high purchase volume (those 2 obviously aren't mutually exclusive) good value per sale (c. £150 is spot on) and wide number of commission paying retailers.
In return we can monetise the site (to a degree that seems to have impressed the very few people we've discussed it with) build a traffic stream and ranking /
PR.
We would take complete care of the site and pay a percentage of all sales.
If it turns out that we aren't chasing rainbows or looking for the moon on a stick we would look to do one site this year.
Hope this helps...