This is exceptionally bad advice. 90% of startups fail, give or take. By far the most likely outcome is that you will be selling this company for less than you put in to it. If you do not give preferred shares to the founder who actually invested, then that person will not be first in line to get their money back.

Example: Alice puts in $250k. Alice and Bob split the company 60/40, common shares. After a year, there's $100k left in the bank, and Alice and Bob decide to call it quits. At this point, Bob leaves with $40k. If Alice had preferred shares, she would get more of her money back.

But even preferred shares are a terrible idea. The right thing is to give the founder a convertible note. That means the founder has debt if the company folds early (and gets his/her money back), and if the company raises a financing round, they just convert on those terms in to the same preferred shares as the subsequent investors.