As you know Social Security is reduced by earnings prior to retirement age.
For 2012 (from http://ssa-custhelp.ssa.gov/app/answers/detail/a_id/236/~/how-work-affects-social-security-retirement-payments )
"If you are under full retirement age for the entire year:
- You can earn $15,120 gross wages or net self-employment a year and not lose any benefits in 2013.
- We will deduct $1 in benefits for every $2 earned above $15,120."
The amount used for this is only wages and earnings - pension, any type IRA distributions, capital gains, rental income and pass through profit from an LLc are not counted. Only net income or wages from the consulting, wages or guaranteed payments from the LLC and any other salary or wages will be used for compute that reduction in social security benefits.
All of the income items except Roth IRA distributions are at least partly taxable.
Pension from a company taxable amount will depend on the type of pension and your contributions after tax, if any. If no after tax amounts were paid in then it will all be taxable. The same rule will apply to traditional IRA distributions.
Except for the pretax contributions everything else (except capital gain) is taxed as ordinary income.
The rate on ordinary income changes as you have more taxable income (after deductions and exemptions). For tables of the rate brackets and percentages please see http://www.forbes.com/sites/kellyphillipserb/2013/01/15/irs-announces-2013-tax-rates-standard-deduction-amounts-and-more/
Capital gain rate also now depends on your income level.
Capital gain rate is zero for the income up to the 15% rate bracket,
Capital gain rate is 15% for the income up to the 33% rate bracket,
Capital gain rate if 20% for income in the 39.3% rate bracket.
(sorry the rules are written to be so complex).
For most taxpayers a 15% rate applies to their capital gain income when the property was held for more than one year.
To summarize only salary, wages, guaranteed payments for services as a partner or LLC member and net income from self employment will be used to reduce the social security benefit.
Only Roth IRA distributions and return of pension or IRA after tax contributions will not be taxable.
Capital gain will have a lower rate than all other (ordinary) income.
Ordinary income rate depends on total of taxable income per the rate charts.
Please ask (reply to expert) if you need more discussion or clarification.