A traphouse refers to any house where drug dealers sell product (typically hard drugs such as crack, meth, or heroin) and/or host clients while they're getting high, often allowing clients to trade sex for drugs in empty rooms. They run the spectrum from clean, relatively well-maintained accommodations run by grandmothers to burned-out shacks with newspaper over the windows and no running water. Gang connections are common but not a prerequisite.
Social workers and public defenders, the good ones who believe in Harm Reduction at least, may meet their clients at traphouses for lack of a better address, and in my experience the addicts allow social services to come inside on the understanding that no one is being reported to the cops and anyone can refuse services.
Even the nicest traphouses are guaranteed to shorten your lifespan. While addicts on the street tend to look out for each other, addicts in a traphouse will often look the other way if someone is about to overdose, either from antipathy, being too high to function, or fear of alerting 911. Your odds of getting shot are high. Your odds of overdosing from something you didn't intend to take (Fentanyl being the worst) are high. Your odds of catching hepatitis, tuberculosis, or HIV are high.
Picture this: A house in the low-rent district, usually a side street where no one will complain about strangers coming at all hours. A big dude keeps watch at the door. You pass him to a kitchen, the table littered with used syringes, the stovetop empty save for a skillet filled with radioactive orange-colored lard that gets reheated and reused over and over to cook meat. A pair of underwear is stuffed into a broken window pane. Anything of value was sold ages ago. If you are a woman trying to sell sex, your looks, age, or hygiene truly don't matter, to the point that some women cover themselves in feces to prevent potential rapists. The dealer usually takes cash, but if you get Social Security benefits can hold onto your Direct Express card until you blow through your monthly allotment.