There is no ban for deleting a single post. In fact deleting your own question or answers when you realize they may not be helpful is encouraged. This will help to keep the site clear.
There is also no ban or other sanction in case you decide to delete your duplicate question but in general it may be better here to leave them as a signpost for other users which may help to find the answer given in the master question to which it will be linked to after closing.
Only in rare cases when we see users deleting many of their posts with no obvious reason this may be considered as vandalism, and it may eventually lead to consequences.
There are even two badges to be earned when deleting you own posts: Disciplined and Peer Pressure
