Naturally, these transfers can take a bit longer than cash accounts from a typical bank which can be wired in a matter of hours.

The rule is that you must have acquired (constructed) unit B with the intent of holding for productive use. 

Fannie Mae generally requires lenders to obtain a two-year history of the borrower’s prior earnings as a means of demonstrating the likelihood that the income will continue to be received.However, a person who has a shorter history of self-employment — 12 to 24 months — may be considered, as long as the borrower’s most recent signed federal income tax returns reflect the receipt of such income as the same (or greater) level in a field that provides the same products or services as the current business or in an occupation in which he or she had similar responsibilities to those undertaken in connection with the current business.

It involves REAL land, and REAL structures erected on the land that are subject to the laws of nature.

The FNMA product used to be a no-brainer because of the rates, but now you can get a 30-yr fixed rate, 30-yr amortization in an LLC.

This is a separate loan product from conventional (Fannie Mae and Freddie Mac loans). 

Is oyster gray "dark grout" or should I go with natural gray?

The 'new' debt service coverage ratio (DSCR) driven products are more attractive, though, IMHO. 30-yr fixed rate, 30-yr term, rates in the 4s (right there / better than banks) and no debt to income ratio BS.

Interest payments are typically made monthly, and most hard money loans don't amortize (because of their short-term nature).

Sound barrier performance is based on density of the product.