When you subdivided the original 146 acres you should have allocated that initial $105K, (plus costs associated with the subdividing process), among the 4 new properties. Simple math suggests a per property cost of about $26 - $27K, but you're not limited to that "simple math" process. If one or more of the parcels is more desirable than the others - better topography for building, a view or stream, road access, utilities to lot line, etc. - then the allocation can be different for each lot.
So, a question for you: did you allocate that basis among the new parcels and include that in the basis of what you sold? If not an amendment of that 2015 income tax return is in order.
Assuming the "simple math" allocation took place each of the remaining parcels has a basis of that $26K - $27K so the sale of the one parcel under contract will result in a long term gain of something like ($117 x 93%)* - $26.5 = $82.3K.
Assuming an AGI before gain of $50K, assuming both children are dependents, assuming you take the standard deduction, assuming there are no other factors to consider like HSA deductions, available tax credits, etc., (are you starting to get the drift that the devil is in the details to what you might consider a simple question?), then you'll have taxable income of about $110.7K and that suggests LTCG tax of around $11K, a "blended" rate of 13%-14%.
If you sell the 2nd parcel too in 2017 that will most likely be taxed at 15%.
Tom Young
*SWAG of net to you after fees
