I don't know what my marginal tax rate will be upon retirement

[Emergo]

People keep saying I have to have an idea of what this should be. But I don't even know where to start. Please help.

[MDM]

You have to estimate your spending in retirement, and the source (e.g., from traditional, Roth, or taxable) of those funds.

Filling out the case study spreadsheet might (or might not) help you organize your thoughts.  The www.i-orp.com planner is another way to get retirement tax rate estimates.

[deborah]

Have you planned your investments for retirement? Let us say - yes, I am going to own 13 houses, and I will live off the rent. I will also have a Roth (whatever that is - I'm Australian)

If yes, what income will you get from taxable investments, and from untaxable investments - $20k a year from my rent, $10k a year from my Roth

Now, I assume that a Roth doesn't get taxed, and your rent does, so you will have to pay tax on your $20k - what is the US marginal rate for that?