I don't think the SDK has rate limiting built in yet, actually starting work on clickup next week.
It really depends on the API, some you can get up and running in a usable capacity in as fast as Stephen mentioned. For someone new to the SDK I'd say at least 4 hours, when I was new to python it was 8 hours for me to get something simple to work but again I was brand new to python.
Where APIs get harder is when you have a bunch of streams, parent and child relationships and some have incremental stream capability. Then you have to figure out the right balance of that with the API limits you have.
The other hard stuff that takes a while is decent documentation, tests, CI (testing multiple versions of python), Discovery process (Sometimes easy if you can hard code it, if you need to dynamically make this it really depends on the API). ie for click up you have custom fields.
I sent you a DM as I'm actually trying to put a clickup tap together right now, and maybe you would like to join with the group that's pitching in to make this happen