There are a lot of considerations like setbacks, lot coverage, parking requirements, height restrictions, floor area ratios, stormwater, utilities, access etc.Assuming you can develop multiple units you could proceed with the development, set aside one unit for your father in law and sell and or rent the remaining units. 

i have one company saying i need $825,000 (thats $147 per sf) coverage for a building of 5,610  square feet, and one company said i ony need $675,000 (thats $120 per sf), it is a building with bricks just for the first like 4 feet then its siding.please let me know    thank you

I tried online and it was getting too time-consuming to get the info and coverage I wanted. 

I'm less interested saving money on coverage than in being covered as well as possible in a catastrophe.My first thought was to go with one of the few companies still offering guaranteed replacement cost coverage.

As you pointed out, it's not comprehensive but it's a great start for folks.I'd like to add to #10 because it feeds into the relationships part of the business.

It provides millions in additional coverage for a nominal amount of money. 

I was looking to get vacant property coverage & builders risk.

You may want to talk with an advisor or someone who can give you a holistic response based on your "comprehensive" personal situation.

(There's an equation, it's called debt service coverage ratio, and basically, a basically net income must be 120% of the mortgage payment.)

Further, if they decide the prior conveyance left a gap in coverage and may result in a defect in the chain of title, then they won't insure the next Purchaser either.