An important thing nobody ever told me:

Don't let a toxic friend stay at your place for more than a week.

People's sense of boundaries has elasticity. Once time stretches on, toxic friends will keep pushing closer to the edge. This is the most tense and dangerous point in any relationship.

I let a close buddy crash at my place for two weeks, and I've been building up more and more resentment—like "he's eating my food, using my stuff, and constantly talking trash about me." Thankfully he's leaving this weekend, otherwise I'm genuinely worried we'd end up throwing hands.