Property

[rangerj]

The basis in the half you purchased is the price you paid plus any expenses related to the purchase, eg attorneys fees. Generally the basis in property acquired by gift is the basis in the hands of the donor r the last preceding owner who had not acquired it by gift (see IRC code section 1015(a)). The basis for a loss is generally limited to the lesser of fair market value at the time of the gift or the adjusted basis of the property prior to the gift. There are some other possibilities depending upon when the gift was made, e.g. on or after September 1 1958 and before 1977 or after 1976 and whether or not gift taxes were paid.

[rangerj]

Check with the county records of real estate transfers. It is common for there to be a transfer tax at X dollars per $1000 paid/sold for the property. Say if the tax was $1 per thousand back in the 1940s, and $20 was paid, then the property was purchased for $20K. Or, there may have been a real estate appraised value for R/E taxes at or about the time your kin bought the property (just before or just after the purchase/sale).  Depreciation, or basis for a sale, are deductions and the burden of proof for a deduction is on you. If you cannot provide a reasonably accurate basis then it should be zero.