When you say "my wife and I are buying the sisters half " does this woman (your wife's aunt I presume) have a currently recorded deed to her half--and is her "half" an actual surveyed out parcel or is it just a result of a will from her dad that stated something like "she gets 1/2 and her brother gets the other 1/2" without delineating property lines??
If she currently has full deed and clear recorded title to her part, SHE needs to get an attorney to draw up the contract for her sale of the property to you. You, if she did not recently do so, need to have it surveyed!! You also need an attorney, to ensure that you get an easment--don't end up landlocked or father-in-law end up landlocked if one half does not have an entrance/exit to public road. You can both use the same attorney, but he has to represent both sides equally.
My sister inherited some property a few years back. 41.4 acres. She wanted to sell it, so my brother and I decided to buy it. She had applied for and recieved full deed and title to the property--said deed was recorded at the county clerk's office.
1st. Brother and I decided how we were going to split the property, which had recently been surveyed in entirety but not in division. We walked it, and decided where the new property lines would be, and drove stakes.
2nd We then had it surveyed for division between he and I. We didn't split it 50/50--I wanted what turned out to survey only 17.4 acres, he wanted the other parcel which surveyed 24 acres.
3rd. Now that my sister knew who was buying exactly how much acreage, she had her attorney draw up the contracts, spelling out the acreage, including a copy of the metes and bounds, referencing that she was keeping mineral rights, and contract stated the selling price. My attorney looked it over, said my brother would need an easement on the contract and in the survey. Had the survey re-done to include access-egress easement. His attorney looked the new contract over said it was good, mine concurred and we paid sister. Took our copies of the signed notarized contracts: "________ did appear before me today with payment in the amount of $XXXXX.XX blah blah blah..for property blah blah blah..." down to the county courthouse to the clerk and filed for deed.