One-person companies can have the same type of retirement plan common at large corporate employers – including Roth 401(k)s. In fact, two of the best plan options are solo 401(k)s and solo Roth 401(k)s.

Their biggest benefit is that they often allow for higher retirement-savings contributions than other plans. They also have less-complicated contribution rules than a Keogh, which offers high contribution potential but may require the expense of an actuary and extra paperwork.

Solo 401(k)s let you put away more than a Simple IRA, which allows a maximum contribution of $11,500 a year for those under 50 and $14,000 for those older, plus up to 3% of income (after adjusting for self-employment tax).

Regular solo and Roth solo 401(k)s also can allow for higher contributions than a Simplified Employee Pension (SEP) IRA at the same income level.

With a solo 401(k) or solo Roth 401(k), for 2009 and 2010 you can put into the plan 100% of your first $16,500 in income from the business (or $22,000, if 50 or older), plus 20% of net profit, until you max out contributions at $49,000 (or $54,500, if you are 50 or older).