Your new account will start with zero feedback. This is somewhat of a disadvantage for a seller in terms of buyer trust.

I've considered opened a second account too. I'm thinking it would be better to keep the account with significant feedback as the selling account and open a new account for buying.

As I recall, you will need to supply a backup source of funding for any new account opened, probably both a credit card and bank account. These accounts must not "touch" your established bank and credit card accounts in any way. I haven't looked at the rules in a couple of years though, and this may have changed. My current account has bank and credit card links; the default source of funds is the balance in the PayPal account. If that is zero, it defaults to the bank account, although I can select the credit card as an alternate source on a purchase by purchase basis.