They are a Chinese company, I think they run around $140/linear foot.

For every 1 foot increment that the lowest floor is below BFE, your rate increases dramatically.

I would walk them, drive them, evaluate what the standard home in that area usually sale for, rent for, and what is the standards for that area(amount of bedrooms, baths, square footage, years built).  

How many square feet is the house?

Less than $1.50 a square foot here in California.  

I'm looking into a 1925 duplex in an "over-and-under" configuration.There are two units, each about 700 square feet, and the downstairs one is partially below ground (there are windows high up on the foundation).  

Again the lender may not like the idea but often if they know the owner is totally out the picture you could have a foot in the door.  

I would want more square footage in the living space, he would be O.K. with that if he were allowed to park the bikes in the house (and, yes, we have had that conversation).

Covered square meters It is customary to insert in the preliminary contract the "metri quadri coperti" of the home being sold and these must be carefully measured.

Trying to apply two or three strategies to just any situation is trying to put a square peg in a round hole, it just won't fit properly.