Can I really do this with my taxes to get a mortgage?
It is illegal to manipulate your income to qualify for a mortgage. In fact, it's a felony. As for lying now and amending later, you would be pretty much guaranteed an audit. The IRS doesn't look kindly on magic 1040X forms that lower tax bills.
Don't manipulate your expenses, but there are things you can do. Home office expense no longer exists as a deduction. If you bought office equipment, furniture, and/or technology you can choose to depreciate it instead of writing it off or taking bonus depreciation. A knowledgeable small business tax preparer can help you with these choices. Deliberately leaving something off is not the way to go. As others have said, that's mortgage fraud and tax fraud. There's a new business deduction this year called QBI. It affects your taxable income but not your AGI. The mortgage company is looking at your AGI.
It is tax fraud to not claim all the income you receive. If is also TAX FRAUD to not claim all the deductions you are eligible include self employment business expenses. If you really read "I need to take the hit and not write off all of my miles, new technology, home office, etc." They are ALL WRONG and TELLING YOU TO COMMIT TAX FRAUD! - why is this tax fraud? Because you have inflated your self employment tax which means you are increasing your future social security benefits. So you are asking - can you file a false tax return and then a few years later file an amendment that drastically changes your business deductions and total taxable income? There is no way that is not going to result in an audit. As well as you have admittedly lied on a tax return which is a felony. That's why Michael Cohen is in jail right now.
Pascal the Gambler
It would be mortgage fraud to misrepresent your income in such a way. It is not only wrong, it is a felony.
Trying to fool the IRS and the mortgage lender is going to end up in a bad way. Don't do it.
Technically, if you intentionally do not write off something that you can, the government may go after you for trying to get more social security benefits than you deserve. (The amount of social security benefits that you will receive later in life is based on the amount of money on which you have paid tax, so a person could try to pay MORE tax to get more social security benefits later, although this would probably be stupid even if wasn't against the law.) However, it's relatively unlikely that they will go after you for this, especially if you amend soon to the correct numbers.