Ykhjuy

I plan to contribute the maximum $6000 to my Roth IRA for 2019 in the next month. However, there is a good possibility I will make over $122,000 dollars with overtime and therefore will be disqualified from contributing.

What happens if I do make over $122,000? Do I have to take the money out?

I prefer this method because there are no decision points based on income.

Contribute to a Traditional IRA

There are no income limits for this. Do this at the same institution where you keep your Roth. Invest the money in a cash sweep account, do not put it in anything interest bearing, and especially, not in a bond or stock.

There are income limits for taking the tax deduction, but that matters not, since you don't want to do that. That makes it a Non-Deductible IRA, and the amount of your contribution will not be taxed when it comes back out, since you already did pay taxes on it. Gains would be taxable, so we're avoiding gains by putting it in a cash sweep account.

Convert to Roth

The very next day, convert the amount in the traditional IRA to Roth. There is no income limit on this either.

There is also no tax, because you are converting money you "already paid taxes on".

Normally, when you convert to Roth, you must treat the converted amount as taxable income, and normally you would aim to do this in a gap year. However, since you are converting from a non-deductible traditional IRA, there is no tax on the amount you contributed (yesterday).

Together these two are the "Roth backdoor" and can be done at any income level (provided your taxable income >= the contribution.)

That may be the simplest option, but there are others.

from non-authoritative source RothIRA.com:

Recharacterize Your Contribution

Ideally you would be able to recharacterize your extra contributions
and any NIA into a Traditional IRA. “Recharacterize” means essentially
“I don’t want these to go toward a Roth, I want them to go to a
Traditional IRA.” This also assumes you would qualify to contribute to
a Traditional IRA for that tax year. This is ideal because you’re
still saving for retirement.

Withdraw Your Contribution Overage

If you don’t qualify for a Traditional IRA (and thus cannot
recharacterize your overage), you can simply withdraw the extra
contribution and any NIA (income earned by the excess contributions).

Apply Your Contribution to a Future Year

You can also apply the excess contribution and NIA to a future year.
You may have to pay a 6 percent tax to the IRS to be able to do this.

One option is to put the money into a non-deductible IRA in January 2019 making sure the custodian knows it is for 2019. Then a few days later do a backdoor Roth conversion.

You will have to pay any taxes on the gains while it is in the non-deductible traditional IRA, but that shouldn't be that much.