Hello Nienna. Welcome to Purrs.
How lovely that you're looking to adopt.
In answer to your query, a number of rescues will offer "trial adoptions" where, if things don't work out, an adoptee can return an animal to the shelter.
However, I'd suggest you need to ask some questions about adoption fees, healthcare and insurance, etc. It might be simpler to meet the cat a few times at the fostered first, and spend time in their company. Remember though that some cats are not displaying their true nature when in rescue and don't really blossom until they're in their forever home.
What can they tell you about your preferred cat's background? How much experience do you have with cats to date, and how comfortable do you feel about your chosen rescue? Gut instinct can tell us much in any situation.
It's no bad thing to be cautious, but on the face of it, the offer of a trial adoption is not a bad one, hence my questions. Sounds like this could be a very exciting for you, coming up.