Conversion FROM Condo to Apartment Building

Condo Association voted to convert from condo association and sell to party converting into apartment rental. Held for less than 1 year when sold/converted back to apartments with 50K gain. Held for only one year so no automatic $250K deferral. And dDoesn't look to be Section 1033 Involuntary Conversion exception. BIL did not structure as Section 1031 at time of sale. Has bought another property. does Section 1031 have to be established prior to sale? Is BIL missing a way to exclude 50K gain either by threshold exclusion and/or rolling gain into basis on new property? Thanks in Advance. Off to look for prior answerrs.

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