How can I find files that only have certain permission for owner?

Start with:

find /path/to/file -user user1 -perm -u+rwx

This means: look for files starting in /path/to/files, owned by user1, where the permissions for group and other can be anything (- in front of the permission string) and the users permissions are only: rwx

To search for files only (no directories) then add -type f.

Also, try some reading. This has great examples: Find tutorial