Spending Large Savings to Build

My husband and I have saved a significant amount of money to build a garage apartment. When we choose to begin the process it will exceed the amount of our total income for the year.

He is the breadwinner, and my income on paper would not be enough to cover non-eligible costs.

The dilemma is then, he will continue to get paid throughout the year, covering food and other non-qualifiying expenses, yet we will technically be spending the equivalant of his yearly income.

First question, would you then advise to claim our entire income?

The code literally lists garages in the description, which leads me to my adjacent inquiry.

Does the law permit me the right to claim the entire building of the garage apartment?

Thank you for your service, time and input.
Sincerely,
K.Foster