There is no adequate reason given for the DEA to have seized Walter White's former residence as they had yet to convict him or even try him for committing any criminal activity. Even RICO (The Racketeer Influenced and Corrupt Organizations Act) would require hearings to determine if Walter's home was both his and an asset which they could attach as part of asset forfeiture. They could not have simply moved Skyler from the home as her filing any number of legal writs or even short selling or quit claiming it to a relative could have prevented this.
The narrative of the series needs to give Walter serious incentives to realize how his drug manufacturing and dealing has adversely effected his family. By showing that they have been forced to move from their home less than six months after he fled the jurisdiction is simply a conceit of that narrative. After all, Walter only "confessed" to certain things over the telephone and given his deteriorating health any minimally skilled attorney could have made the case that his mental state was impaired and that he had no idea what he was saying.
The show is also incorrect as the DEA cannot "RICO" anything. Any prosecutorial decisions made at the US federal level come from the US Attorney's office or from the Attorney General.While the DEA could recommend that the US Attorney seize Walt's assets, without formally criminal charges having been filed and without clear evidence that his familial home was involved in the drug business, this would have been a tough road for them to travel. Saul Goodman as a skilled litigator should have known this and should not have made such a glaring legal error.