"Taxpayer" & "spouse" are a newly married couple, in their 50s (not their first marriages). Both taxpayer and spouse own their own, separate residences prior to and at the start of the marriage. Both houses have large appreciation, above and beyond the $250k exclusion taxpayer and spouse are separately allowed under Sec 121. Taxpayer owns house "A" and spouse owns house "B". Both taxpayer and spouse are flexible.
I have suggested that taxpayer move into house B and begin using it as a principal residence. They would sell house B after 2-3 years. I am pretty confident they'd qualify for a $500k exclusion on house B at the time of sale, assuming a joint return. Then, both taxpayer and spouse would move into house A and begin using it as a principal residence.
Would their max potential $500k exclusion on house A be reduced for nonqualified use under Sec 121(b)(5)(C)? My read says yes, it would. However, it appears they still come out well ahead with this strategy.