Contrary to popular belief, these animals do not need to be allowed everywhere their owner goes. 

All of this to say, unless the agent has a proven track record for renting similar places or a network of potential customers (read: international companies regularly relocating workers), I wouldn't bother with them.

Make some more calls - call an agent or two on the other side of your state, who may see you as bonus business, not a local customer to try and steer into a full replacement policy, unless, you really want to build a new home right where your rental is on the very outside chance there's a total loss. 

How did things go down and how popular is it?

i have been using an excel spreadsheet i custom built for what we need)

(Related: We all know interest rates will rise sooner or later, but exactly when is anyone's guess)So the only thing you can really do is choose based on your customers' preferences today, since "money today is worth more than money tomorrow" anyway.

They wanted it under our names only and they would only do it with existing customers.

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Until I realized I need to utilize my creativity, ingenuity, number crunching forte, ability to sell and impeccable customer service skills.  

It is speculative in that you are not building a custom home for a specific buyer, just speculating (obviously based on market analysis) that there are buyers in the area looking for what you're going to provide.