A careful watching of the movie shows that the Beckers were partially wrong in their assessment of Percy, which explains why their scheme went completely off the rails:
They assume he is completely friendless but he has both online friends and few, but very devoted real world friends, such as Jodie and Crispin.
They assume Percy is unprepared for a sexually active life, but Percy is shown to actually be able to get to have sex with someone on his own when, absent one Ibuprofen-induced road-stop, he would've had sex with Natalie within the hour of reconnecting with her.
The sale of the house may have triggered a fresh tax assessment, which means Sara and Jim won't be paying higher property taxes. Or, the couple could simply appeal to their local government and have their property taxes re-assessed and lowered.
Jodie used his connections to get Maddie's property taxes raised as retaliation for her hurting Percy. This doesn't affect Maddie because she already sold the house… but she sold it to Sara and Jim, who could now be saddled with the higher taxes.
If Jodie does not go back to said connections and have them reverse their actions, it'll backfire on them. If it comes out that they raised property taxes as an act of retaliation—that misses its target and hits a married couple expecting a child—it could lead to bad publicity. It might even trigger a civil or criminal action against them.
