Hi James and welcome to iGP
The star rating is an indication of the level of the staff member relative to YOUR level. It is not possible to employ a member of staff with more than 5 stars because their level will be higher than your manager level. The highest star rating you will be able to employ is 5 stars.
The Doctor who is employed by your competitor appears to be 6 stars when viewed from your account because you are a lower manager level than your competitor. When your competitor views that same Doctor from his account the star rating will be 5 or below.
Regarding low level Talent 20 drivers... These are usually generated from a high level manager's Youth Academy. You could try posting a "Wanted" on the marketplace subforum or speak directly to the Elite managers in your league.
I recommend you read the
Rules & Regulations most of the basics are explained here.