If they are cagey about certain things you may have stumbled over something you may not find acceptable. If they are not open, you are advised not to join. At one time it was acceptable to not allow the new member to meet the rest of the coven until they were initiated. This was due to the amount of trouble that an infiltrator from the authorities could cause. This is no longer the case.
Personality clashes can be damaging, and even highly destructive, in an intense magical situation.
If you do not get along with someone, don't join. In some covens the group decides collectively who will be accepted as a member. In this case if you do not get on with someone you will probably not be accepted anyway. It is generally held acceptable to charge for incidental costs such as cakes, wine, candles etc. If someone is making a profit, this is abuse.