We have a roommate who consistently does not pay her rent on time. We are all signed on one lease, and the landlord is unwilling to take her off. This month, she decided to spend 1,500 on a condo for her birthday instead of paying the $400 she owes us. The money is laying on her dresser, can we legally take $400 of it? If not, what are our options?
This (as always) depends on jurisdiction, but usually - No, just taking the money is not legal..
In most jurisdictions, if you have a claim (the rent, in your case) against a debtor , and the debtor does not pay, you are not allowed to take any enforcement action (taking property, coercing the debtor) yourself.
Instead, you must obtain a court or administrative judgement confirming your claim. Even then, often only a court officer or the police may actually enforce payment of the debt.
This is mostly to protect the debtor from unwarranted enforcement action (such as taking more than you are owed, or collecting a disputed debt).
For example, in Germany, to enforce a debt the creditor must first obtain what is called a Vollstreckungstitel or just Titel (title) - an official document confirming that there is an outstanding claim. This is on top of any contracts already existing. A Titel is obtained either through a regular court judgment, or through an abbreviated, administrative process called Mahnverfahren (essentially, you ask the court to send the debtor a letter about your claim, and if the debtor does not file an objection, you get the Titel).
Once you have a Titel, the creditor can enforce it any time they choose (with a Titel, the statute of limiation is extended from the usual three years to 30 years). However, actual enforcement must be performed by an officer of the court (Gerichtsvollzieher). Only they may do things such as collecting the debtors property, force open doors and even imprison uncooperative debtors.
I don't know the exact situation in the USA, but I believe it is roughly similar. For example, the equivalent of a Vollstreckungstitel is a Writ of execution.
No, it's not "legal" to take money from someone, even if it's owed...unless a court tells you it's ok.