Contract Help: Selling Part of Lot w/Duplex and House on it.

[Eric Gabriel]

ADVICE - CONTRACT NOT SIGNED

I got a contract from a buyer who wants to buy my duplex.  Here is the deal in a nutshell.  Let me know if it is a good deal for a row house development in Portland, Oregon.

1. I will carry a note for 9-12 months while the developer goes to the city of Portland to get permits and subdivide the duplex off of the main house.  The buyer will pay $5000/mo during the permit process.  I also get to continue collecting rent during that process which is $2500/mo.

2. Once the permits have been gotten, the buyer will exercise their write to buy the property for $500,000.  (earnest money is $5000) so they will pay $495,000.  Once the money is in my pocket, they will demolish the duplex since it can't be as close to the house as it is AND be on its own tax lot.  

3. The buyer will develop 3 luxury townhouses.  The townhouses across the street are selling for $750,000 each.  There are 8 of them.  

My question is, does the contract have anything missing that will hinder this process or put me at risk?

One question about selling is, should I sell the triplex all together, or is it better to sell just the duplex, or should I just keep the rental income?

The house by itself, if divided from the duplex, as-is, would be worth at least $350K, fixed up $500K.