Also you may want to add some language that if the roof repair date (passed permit Final inspection) gets delayed and causes you to pay an addional fee for a rate lock extension, the seller credits you at closing. 

Leverage the existing networks folks have.This requires you to develop a relationship and extensively network.

It’s competitive and requires extensive due dilligence but it’s here.

Usually go with non refundable down payment,  some type of monthly credit towards their purchase (only if negotiated ), buyer responsible for all repairs ( assuming home is in good condition when they are buying it) and if they are not able to execute at the end of the lease term offer an extension period with possibly a little more down payment. 

So from having a contractor who fool us with the extension when we asked for a 3rd bedroom, We were able to get it done for much less than expected.

They are going to be asking for another extension on the closing date, but I'm not sure if it's a good idea to continue to move forward. 

The home me and the Mrs. have settled on, is yet to be built but we like the model and a similar home that was recently built that we have extensively walked through.Now, here is the catch.

There is usually a clause in the P&S or addendum to the effect that if the seller needs time to remove any defects in title, deliver possession or make the premises conform, you agree to give them an extension and if they are unable to perform by the expiration of the extension, the seller will refund buyer's EM and the contract will be void with no recourse to either party.

There is a guy on here who posted a very extensive thread about a SoCal development project, he might be a good contact for you.  

Preventing further damage is easy and the good news is that even if that damage is extensive, it still isn't expensive.