How many appointments does it take to know if a therapist is a good fit?
This is a serious answer even if it doesn’t sound like it.
How many dates do you need to have with another adult before you decide you want to keep dating?
Most people will say “one.” Should be plenty unless you’re seriously missing something, which can obviously happen, like the person is married. Or has a horrible temper, or gets too jealous. That first date is pretty telling, but something unexpected could easily come up, soon, or way down the line.
Except for the first impression part, it’s different with therapists. You can get a feeling, fast, about the likely fit, because it’s improbable anything shocking is going to come up later. Besides, therapists are supposed to be able to adjust to you, without a lot of vice versa.
Unlike dating, it’s a relationship for a carefully managed, well-boundaried single hour every week or so, with a person who’s trained and who has experience in doing what they’re doing, probably for thousands of hours, without getting into too much trouble.
Sure, you can get a lemon or a stinker once in a while, but the average therapist, provided you feel comfortable, is most likely just fine.