Will I get penalized by Upwork? I'm just not sure I want this job until I actually get some practice on it. (Data entry.) I'm not sure it's going to be worth my time. Can I go for it?
re: "What happens if I accept an hourly job and then decide I don't want it?"
Clients can cancel a contract any time.
You don't even need to provide a reason.
re: "Will I get penalized by Upwork?"
re: "I'm just not sure I want this job until I actually get some practice on it. (Data entry.) I'm not sure it's going to be worth my time. Can I go for it?"
You can "go for it" in terms of actually trying to do the job.
Or you can "go for it" in terms of quitting immediately.
Upwork won't penalize you either way.
The CLIENT has an opportunity to leave feedback.
If you quit immediately, the client might do nothing.
Or the client may leave feedback. If no money has been earned, then no public feedback will appear on your profile page, but there IS a chance that the client will leave private feedback. There is also the possibility that the client won't leave any feedback at all. If the client DOES leave private feedback, then there is a chance that the feedback will be negative... in which case, it could affect your JSS negatively.
But jobs are weighted by dollar amount in terms of how much they impact JSS. If you earned nothing or very little on a job... how much will it impact JSS? I don't think the impact on JSS is enough to worry about when compared to the importance of NOT doing a job that isn't right for you.
If this job is not right for you, then YOU ARE DOING THE CLIENT A FAVOR if you quit now, rather than hang around for a while.