The hardest part is sorting through them.

From my understanding these are SEC rules and what most RE crowdfunding, startup crowdfunding, and third-party verification services (ex: verifyinvestor) all use.

Make a offer where both party can see reasonable and your numbers work for you and leave it at that.

In house is cheaper but takes a lot of time to put together so depending on what value you put on your time- may be worth having a third party do it. 

The boundaries of a neighborhood can be larger streets, tracks, parks, etc.A house as close as possible in features (beds, baths), size, etc.Using the same financing method, with an arms-length transaction.Once you've found the right comps, then you have to make adjustments to them based on all of those features to get an accurate value for your property.I used to use a spreadsheet for that, until I built this tool: www.reikit.com/compsThe tool uses Zillow data for lookups, but usually I go in with my own set of comps from my realtors then use the tool for adjustments.The hard part is getting the comps, though, and MLS is always going to be king.Cheers!

I didn't see how having both parties try to outbid each other face to face would be helpful, and that it would kill the deal for anyone, most likely.

We have an assignable contract for a purchase and an interested party in a foreign country.

I know I would not want to live next to a vacation rental that rents to 20 or so people at a time and the pool party is still going on at two in the morning!

And everything is in writing signed by both parties. 

@David Green you will certainly want to send 1099's to all necessary parties.