Is it true that during the Salem witch trials, the "afflicted girls" would get people hanged, and then their parents would buy up (or be awarded) the land?
No, although its more complicated than that. A lot of people believe this myth that the Salem Witch Trials occurred over land disputes and efforts to steal property. It has a truthiness sense to it, but land went to the executed victims' legal heirs. In fact, prisoners sentenced to death even edited their wills from jail, like George Jacobs Sr. who removed his granddaughter after she confessed to witchcraft but added her back in when she recanted. This narrative often comes up in the case of Giles Corey, who infamously stood mute at his trial and died by pressing. Its often said that Corey refused to acknowledge the court's authority to hold the trial and by refusing to answer, the trial could not proceed and therefore his land could not be taken from his sons. The first half is true, Corey refused to answer and the trial stopped. However, the court wouldn't have been able to take his land regardless since his will dictated his land to his sons. Corey was pressed to death, meaning they laid rocks on top of his 80 year old body to force him to speak and ultimately suffocated him with the weight on his chest. Land was never at issue.
Where did land come into it? The families of the accusers and the afflicted girls likely had political motivations. While those motivations involved land, such as the Putnam family's rapid economic decline as dividing property down generations left plots too small for the next generation to live off, they probably never expected to steal land. Land disputes over boundary lines could have aided tensions with particular neighbors and families, but any switch in ownership would have been an indirect path with too many variables to guarantee an accusation against Rebecca Nurse led to Thomas Putnam receiving 300 acres.
Moveable goods/property did come into play with Sherriff George Corwin. At the time you needed to pay jail fees, essentially you rented out the space you took up in jail, the chains that held you, food, etc. Corwin collected those fees, often by confiscating property. He also took more goods than owed, especially from condemned victims. John & Elizabeth Procter were wealthier residents of Salem, and both faced accusations and the court found them guilty. However, Elizabeth was pregnant so her execution was delayed. By luck, her pregnancy lasted beyond the height of the trials and the governor reprieved her sentence. Corwin already looted their home to cover their fees and she returned to poverty. Also, Corwin's uncle Jonathan, the magistrate who signed the first warrants and had a hand in almost every case; and the father-in-laws from George's from his first and second marriages were appointed to the Court of Oyer and Terminer that heard the witch trials. Actually, 8 of the 9 appointed judges were somehow related through marriages. Its like if my uncle sent you to jail and then I get to go through your house to take enough stuff to cover your jail fees and no one watches me. Sherriff Corwin never faced consequences for this.
Land also came into play regarding the Maine frontier. Massachusetts colonists kept pushing north over the 17th century. A lot of families- especially elite families that included judges- speculated land. Magistrates like Jonathan Corwin and John Hathorne invested fortunes in purchasing Maine land. The Indigenous population resisted, regularly raiding English settlements. There's a long history tied to this violence and it intersected with Puritan suspicions that Indigenous people allied with Satan to destroy their shining Kingdom of God being created on earth (the Spanish, the French, the Pope, and just about any non-Puritan was involved in this conspiracy). God's chosen people, the Puritans and only the Puritans (but also definitely not all Puritans) needed to prove their commitment to the covenant by enforcing their religious beliefs on their community, such as 'Thou shalt not suffer a witch to live.' If an individual or community faltered in their commitment to God, providential judgment would rain down on them through extreme weather, warfare, disease, and just about any misfortune. The judges are appointed to the Court, their personal wealth and property are threatened by possibly Satanic forces, and its their God-directed mission to root out witches from their community. Its easy to dismiss their motivation as solely greed- their land is in danger and they're attacking the enemy team through these trials- but its also wrapped up in their religiosity- good Puritans get wealth but need to stop witches to be a good Puritan. This religio-economic motivation played a key role, but this unfolding property drama occurred over decades surround 1692 and far away from Salem. Even when land is mentioned in relation to Salem, the deeply personal and political motivations are hidden by time and space.
For more- Emerson W. Baker's A Storm of Witchcraft is by far the best on Salem generally and also details the judge's as key players with frontier related anxieties. Mary Beth Norton's In the Devil's Snare is a phenomenal look at how violence on the Maine frontier shaped the Salem Witch Trials. Paul Boyer and Stephen Nissenbaum's Salem Possessed is a classic work that dives into the social and political motivations behind the outbreak of accusations.