1. If a reader subscribes to your program Maxifi, is there any reason that he or she should also subscribe to your other website, maximize my social security?
2. When calculating income for which social security payments are taxed, what is defined as "income"? Is it simply AGI, or is it 'earned income" eg. W-2 and/or self-employed earnings? Could individuals with enough passive income to exceed the limits for taxes to kick in avoid paying income tax on SS by earning less?
No, you wouldn't need to subscribe to both programs. Maxifi has all of the features of the basic maximize my social security software program, plus many additional features (https://maxifiplanner.com/retirement-planning-maxifi).
Only earned income counts for Social Security purposes. For employed individuals, the amount shown on their W-2 form in the block labeled 'Social Security Wages' is the countable amount. For self-employed individuals, their net profit as calculated on either Schedule C, or Schedule F, or Schedule K-1, is carried over to Schedule SE, and the countable amount is the amount on which they pay self-employment tax (i.e. basically 92.35% of the total net profits from Schedules C, F, and K-1.
No other type of income is subject to Social Security taxes, and you cannot voluntarily pay more Social Security tax than you owe in order to earn Social Security credits or increase your benefit rate.