The self-employed can set up this version of a traditional IRA themselves. You will reduce your taxable income for your efforts, and the contribution limits are much higher than for traditional IRAs - 20 percent of income, or $52,000 (whichever is less) in 2014. Consult IRS Publication 560 for more details.

If money is tight, a traditional IRA or a Roth IRA will probably give you enough room to save, and might be easier if you already have accounts set up. Each currently offers annual contribution limits of $5,500 (plus an extra $1,000 for people over 50).

The choice becomes whether you want to get a tax break now, with a traditional IRA, or have tax-free earnings with a Roth. You cannot fully fund both at the same time; CPA Medows suggests using a Roth whenever possible.

CONTRIBUTE DIFFERENTLY

But with freelance cash so inherently erratic, how can you contribute enough retirement money?

Brooklyn magician Evan Paquette is a fan of personal-finance expert Ramit Sethi's "envelope" system of apportioning percentages of whatever money comes in to different goals, like basic expenses, entertainment, or retirement saving.

Most financial institutions allow you to set up an automatic withdrawal into a retirement account, or they can send you a digital reminder to make a contribution each month or at certain times of the year.

"That way, whether you're making $100 a month or $10,000 a month, money is still getting put towards the retirement goal," says Paquette, 30, who uses a SEP-IRA to house his retirement assets. "Even if it's only $5, at least it's something."

Retirement experts are looking for ways to make this automation easier for non-workplace savers. One idea before Congress now is an "automatic IRA" that citizens would have to opt out of, rather than figure out for themselves.

This has worked well in the United Kingdom, says Shlomo Benartzi, a professor at the UCLA Anderson School of Management and chief behavioral economist for Allianz Global Investors. California has passed such legislation at the state level, although it has not yet taken effect.